the game immediately crashes after destroying a new employed villager's job site block,
to recreate:
1) Spawn a Nitwit/Unempolyed Villager with spawn egg (or commands)
2) Place a job site block (such as a composter, I've tried it with blast furnaces, composters, and lecterns)
3) Once the villager has changed profession, destroy the block
4) Game will crash.

Crash report:
---- Minecraft Crash Report ----
// This doesn't make any sense!

Time: 3/17/19 11:32 AM
Description: Ticking entity

java.util.NoSuchElementException: No value present
at java.util.Optional.get(Optional.java:135)
at ako.c(SourceFile:54)
at ako.g(SourceFile:17)
at ajk.e(SourceFile:43)
at ajk$$Lambda$3014/822550055.test(Unknown Source)
at java.util.stream.MatchOps$1MatchSink.accept(MatchOps.java:90)
at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175)
at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
at java.util.ArrayList$ArrayListSpliterator.tryAdvance(ArrayList.java:1351)
at java.util.stream.ReferencePipeline.forEachWithCancel(ReferencePipeline.java:126)
at java.util.stream.AbstractPipeline.copyIntoWithCancel(AbstractPipeline.java:529)
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:516)
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:502)
at java.util.stream.MatchOps$MatchOp.evaluateSequential(MatchOps.java:230)
at java.util.stream.MatchOps$MatchOp.evaluateSequential(MatchOps.java:196)
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
at java.util.stream.ReferencePipeline.anyMatch(ReferencePipeline.java:449)
at ajk.g(SourceFile:43)
at ajf.c(SourceFile:52)
at aiu.b(SourceFile:185)
at aiu$$Lambda$3012/751411053.accept(Unknown Source)
at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184)
at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175)
at java.util.Iterator.forEachRemaining(Iterator.java:116)
at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)
at java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:580)
at java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:270)
at java.util.HashMap$ValueSpliterator.forEachRemaining(HashMap.java:1612)
at java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:580)
at java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:270)
at java.util.TreeMap$ValueSpliterator.forEachRemaining(TreeMap.java:2893)
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:512)
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:502)
at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)
at aiu.a(SourceFile:185)
at aua.K(SourceFile:238)
at aig.cW(SourceFile:622)
at aif.k(SourceFile:2202)
at aig.k(SourceFile:478)
at ahu.k(SourceFile:141)
at aif.h(SourceFile:2051)
at aig.h(SourceFile:292)
at vc.a(SourceFile:578)
at vc$$Lambda$2801/1838446809.accept(Unknown Source)
at bfx.a(SourceFile:668)
at vc.a(SourceFile:381)
at net.minecraft.server.MinecraftServer.b(SourceFile:816)
at net.minecraft.server.MinecraftServer.a(SourceFile:755)
at dwb.a(SourceFile:128)
at net.minecraft.server.MinecraftServer.run(SourceFile:630)
at java.lang.Thread.run(Thread.java:745)

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

– Head –
Thread: Server thread
Stacktrace:
at java.util.Optional.get(Optional.java:135)
at ako.c(SourceFile:54)
at ako.g(SourceFile:17)
at ajk.e(SourceFile:43)
at ajk$$Lambda$3014/822550055.test(Unknown Source)
at java.util.stream.MatchOps$1MatchSink.accept(MatchOps.java:90)
at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175)
at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
at java.util.ArrayList$ArrayListSpliterator.tryAdvance(ArrayList.java:1351)
at java.util.stream.ReferencePipeline.forEachWithCancel(ReferencePipeline.java:126)
at java.util.stream.AbstractPipeline.copyIntoWithCancel(AbstractPipeline.java:529)
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:516)
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:502)
at java.util.stream.MatchOps$MatchOp.evaluateSequential(MatchOps.java:230)
at java.util.stream.MatchOps$MatchOp.evaluateSequential(MatchOps.java:196)
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
at java.util.stream.ReferencePipeline.anyMatch(ReferencePipeline.java:449)
at ajk.g(SourceFile:43)
at ajf.c(SourceFile:52)
at aiu.b(SourceFile:185)
at aiu$$Lambda$3012/751411053.accept(Unknown Source)
at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184)
at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175)
at java.util.Iterator.forEachRemaining(Iterator.java:116)
at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)
at java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:580)
at java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:270)
at java.util.HashMap$ValueSpliterator.forEachRemaining(HashMap.java:1612)
at java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:580)
at java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:270)
at java.util.TreeMap$ValueSpliterator.forEachRemaining(TreeMap.java:2893)
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:512)
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:502)
at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)
at aiu.a(SourceFile:185)
at aua.K(SourceFile:238)
at aig.cW(SourceFile:622)
at aif.k(SourceFile:2202)
at aig.k(SourceFile:478)
at ahu.k(SourceFile:141)
at aif.h(SourceFile:2051)
at aig.h(SourceFile:292)
at vc.a(SourceFile:578)
at vc$$Lambda$2801/1838446809.accept(Unknown Source)

– Entity being ticked –
Details:
Entity Type: minecraft:villager (aua)
Entity ID: 185376
Entity Name: Villager
Entity's Exact location: 161.50, 4.00, -392.50
Entity's Block location: World: (161,4,-393), Chunk: (at 1,0,7 in 10,-25; contains blocks 160,0,-400 to 175,255,-385), Region: (0,-1; contains chunks 0,-32 to 31,-1, blocks 0,0,-512 to 511,255,-1)
Entity's Momentum: 0.00, -0.08, 0.00
Entity's Passengers: []
Entity's Vehicle: ~_ERROR~ NullPointerException: null
Stacktrace:
at bfx.a(SourceFile:668)
at vc.a(SourceFile:381)

– Affected level –
Details:
Level name: New Worldeeeeeeeeeee
All players: 1 total; [vd['MasterDogee'/16, l='New Worldeeeeeeeeeee', x=158.71, y=6.07, z=-392.57]]
Chunk stats: ServerChunkCache: 3375
Level seed: 6889265257471209185
Level generator: ID 01 - flat, ver 0. Features enabled: true
Level generator options: {}
Level spawn location: World: (64,4,32), Chunk: (at 0,0,0 in 4,2; contains blocks 64,0,32 to 79,255,47), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 263033 game time, 3897 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 1 (now: false), thunder time: 1 (now: false)
Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
at net.minecraft.server.MinecraftServer.b(SourceFile:816)
at net.minecraft.server.MinecraftServer.a(SourceFile:755)
at dwb.a(SourceFile:128)
at net.minecraft.server.MinecraftServer.run(SourceFile:630)
at java.lang.Thread.run(Thread.java:745)

– System Details –
Details:
Minecraft Version: 19w11b
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_51, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 878913784 bytes (838 MB) / 2046820352 bytes (1952 MB) up to 2147483648 bytes (2048 MB)
JVM Flags: 9 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xss1M -Xmx2G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
Player Count: 1 / 8; [vd['MasterDogee'/16, l='New Worldeeeeeeeeeee', x=158.71, y=6.07, z=-392.57]]
Data Packs: vanilla
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.