Occurred on old/updated world. Save on disk. No longer in the Select World list.
Crash report
17w47b\: [^crash-2017-11-23_12.40.02-server.txt]
Description: Ticking player
java.lang.ClassCastException: arw cannot be cast to aru
at ayn.l(SourceFile:220)
at ayn.j(SourceFile:207)
at aru.a(SourceFile:75)
at qo.b(SourceFile:235)
at qo.a(SourceFile:92)
at qn.H_(SourceFile:307)
at aqc.a(SourceFile:1564)
at ql.a(SourceFile:704)
at aqc.h(SourceFile:1540)
at ql.l(SourceFile:560)
at aqc.k(SourceFile:1405)
at ql.k(SourceFile:537)
at net.minecraft.server.MinecraftServer.w(SourceFile:656)
at net.minecraft.server.MinecraftServer.v(SourceFile:584)
at ckv.v(SourceFile:152)
at net.minecraft.server.MinecraftServer.run(SourceFile:489)
at java.lang.Thread.run(Unknown Source)Description: Ticking player
java.lang.ClassCastException: arw cannot be cast to aru
at ayn.l(SourceFile:220)
at ayn.j(SourceFile:207)
at aru.a(SourceFile:75)
at qo.b(SourceFile:235)
at qo.a(SourceFile:92)
at qn.H_(SourceFile:307)
at aqc.a(SourceFile:1564)
at ql.a(SourceFile:704)
at aqc.h(SourceFile:1540)
at ql.l(SourceFile:560)
at aqc.k(SourceFile:1405)
at ql.k(SourceFile:537)
at net.minecraft.server.MinecraftServer.w(SourceFile:656)
at net.minecraft.server.MinecraftServer.v(SourceFile:584)
at ckv.v(SourceFile:152)
at net.minecraft.server.MinecraftServer.run(SourceFile:489)
at java.lang.Thread.run(Unknown Source)
Cannot reproduce.