When I try to hook a fish the server now generates this error in the console:

[Server thread/FATAL]: Error executing task on Server
java.lang.NullPointerException: null.

 [16:48:45] [Server thread/FATAL]: Error executing task on Server
java.lang.NullPointerException: null
at be.b(SourceFile:183) ~[server.jar:?]
at bi.a(SourceFile:32) ~[server.jar:?]
at bdo.b(SourceFile:478) ~[server.jar:?]
at biv.a(SourceFile:23) ~[server.jar:?]
at bjh.a(SourceFile:212) ~[server.jar:?]
at yv.a(SourceFile:273) ~[server.jar:?]
at zl.a(SourceFile:1000) ~[server.jar:?]
at sp.a(SourceFile:31) ~[server.jar:?]
at sp.a(SourceFile:9) ~[server.jar:?]
at nh.a(SourceFile:21) ~[server.jar:?]
at uo.run(SourceFile:18) ~[server.jar:?]
at alu.c(SourceFile:144) [server.jar:?]
at aly.c(SourceFile:23) [server.jar:?]
at net.minecraft.server.MinecraftServer.b(SourceFile:789) [server.jar:?]
at net.minecraft.server.MinecraftServer.c(SourceFile:159) [server.jar:?]
at alu.w(SourceFile:118) [server.jar:?]
at net.minecraft.server.MinecraftServer.bc(SourceFile:771) [server.jar:?]
at net.minecraft.server.MinecraftServer.w(SourceFile:765) [server.jar:?]
at alu.bl(SourceFile:103) [server.jar:?]
at net.minecraft.server.MinecraftServer.v(SourceFile:749) [server.jar:?]
at net.minecraft.server.MinecraftServer.run(SourceFile:702) [server.jar:?]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_181]

Also the server crashed shortly after.