I was setting the block beneath my player to end gateway, then I summoned a minecart above it, watching it fall through, when I went to the other side, I went to open the minecart, but it didn't open. I then walked into the minecart and crashed. Here is the following crash report.

EDIT: heres what the crash report is for those not wishing to download attachment:

---- Minecraft Crash Report ----
// I feel sad now

Time: 12/08/15 11:03 PM
Description: Exception ticking world entities

java.lang.NullPointerException: Exception ticking world entities
at ayd.a(SourceFile:375)
at lc.b(SourceFile:40)
at agc.c(SourceFile:889)
at lg.c(SourceFile:867)
at agc.j(SourceFile:1305)
at lg.j(SourceFile:481)
at net.minecraft.server.MinecraftServer.D(SourceFile:625)
at net.minecraft.server.MinecraftServer.C(SourceFile:553)
at bud.C(SourceFile:152)
at net.minecraft.server.MinecraftServer.run(SourceFile:457)
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 –
Stacktrace:
at ayd.a(SourceFile:375)
at lc.b(SourceFile:40)
at agc.c(SourceFile:889)
at lg.c(SourceFile:867)
at agc.j(SourceFile:1305)
at lg.j(SourceFile:481)

– Affected level –
Details:
Level name: New World7
All players: 1 total; [lh['BRO_MAHO_101'/222, l='New World7', x=639.45, y=57.00, z=794.94]]
Chunk stats: ServerChunkCache: 652 Drop: 0
Level seed: -6325844678662530134
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: 0.00,0.00,0.00 - World: (0,0,0), Chunk: (at 0,0,0 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 0 game time, 0 day time
Level dimension: 0
Level storage version: 0x00000 - Unknown?
Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
Level game mode: ~_ERROR~ NullPointerException: null
Stacktrace:
at net.minecraft.server.MinecraftServer.D(SourceFile:625)
at net.minecraft.server.MinecraftServer.C(SourceFile:553)
at bud.C(SourceFile:152)
at net.minecraft.server.MinecraftServer.run(SourceFile:457)
at java.lang.Thread.run(Thread.java:745)

– System Details –
Details:
Minecraft Version: 15w33a
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 212316456 bytes (202 MB) / 541290496 bytes (516 MB) up to 1060372480 bytes (1011 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
Profiler Position: N/A (disabled)
Player Count: 1 / 8; [lh['BRO_MAHO_101'/222, l='New World7', x=639.45, y=57.00, z=794.94]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.