Can't play some custom maps.

Client log

[16:21:05 INFO]: Client> [16:21:05] [Client thread/INFO]: Attempt 1...
[16:27:40 INFO]: Client> [16:27:40] [Server thread/INFO]: Starting integrated minecraft server version 14w20b
[16:27:40 INFO]: Client> [16:27:40] [Server thread/INFO]: Generating keypair
[16:27:40 INFO]: Client> Oh noooo
[16:27:40 INFO]: Client> [16:27:40] [Server thread/INFO]: Preparing start region for level 0
[16:27:42 INFO]: Client> [16:27:42] [Server thread/INFO]: Preparing spawn area: 25%
[16:27:43 INFO]: Client> [16:27:43] [Server thread/INFO]: Preparing spawn area: 62%
[16:27:43 INFO]: Client> [16:27:43] [Server thread/INFO]: Changing view distance to 12, from 10
[16:27:44 INFO]: Client> [16:27:44] [Server thread/INFO]: NekoJonez[local:E:debfe523] logged in with entity id 22 at (95.5, 55.75, -0.5)
[16:27:44 INFO]: Client> [16:27:44] [Server thread/INFO]: NekoJonez joined the game
[16:27:45 INFO]: Client> [16:27:45] [Server thread/ERROR]: Couldn't load chunk
[16:27:45 INFO]: Client> s: Loading entity NBT
[16:27:45 INFO]: Client> 	at ty.f(SourceFile:1160) ~[14w20b.jar:?]
[16:27:45 INFO]: Client> 	at ue.a(SourceFile:158) ~[14w20b.jar:?]
[16:27:45 INFO]: Client> 	at ayu.a(SourceFile:291) ~[14w20b.jar:?]
[16:27:45 INFO]: Client> 	at ayu.a(SourceFile:81) ~[14w20b.jar:?]
[16:27:45 INFO]: Client> 	at ayu.a(SourceFile:69) ~[14w20b.jar:?]
[16:27:45 INFO]: Client> 	at om.f(SourceFile:130) [14w20b.jar:?]
[16:27:45 INFO]: Client> 	at om.c(SourceFile:81) [14w20b.jar:?]
[16:27:45 INFO]: Client> 	at ol.<init>(SourceFile:36) [14w20b.jar:?]
[16:27:45 INFO]: Client> 	at ok.a(SourceFile:228) [14w20b.jar:?]
[16:27:45 INFO]: Client> 	at ok.a(SourceFile:265) [14w20b.jar:?]
[16:27:45 INFO]: Client> 	at qb.a(SourceFile:226) [14w20b.jar:?]
[16:27:45 INFO]: Client> 	at qb.c(SourceFile:278) [14w20b.jar:?]
[16:27:45 INFO]: Client> 	at qb.a(SourceFile:133) [14w20b.jar:?]
[16:27:45 INFO]: Client> 	at ph.c(SourceFile:87) [14w20b.jar:?]
[16:27:45 INFO]: Client> 	at ph.a(SourceFile:52) [14w20b.jar:?]
[16:27:45 INFO]: Client> 	at fq.a(SourceFile:174) [14w20b.jar:?]
[16:27:45 INFO]: Client> 	at ow.c(SourceFile:134) [14w20b.jar:?]
[16:27:45 INFO]: Client> 	at net.minecraft.server.MinecraftServer.w(SourceFile:580) [14w20b.jar:?]
[16:27:45 INFO]: Client> 	at net.minecraft.server.MinecraftServer.v(SourceFile:496) [14w20b.jar:?]
[16:27:45 INFO]: Client> 	at clk.v(SourceFile:132) [14w20b.jar:?]
[16:27:45 INFO]: Client> 	at net.minecraft.server.MinecraftServer.run(SourceFile:412) [14w20b.jar:?]
[16:27:45 INFO]: Client> 	at nd.run(SourceFile:682) [14w20b.jar:?]
[16:27:45 INFO]: Client> Caused by: java.lang.NullPointerException: The validated object is null
[16:27:45 INFO]: Client> 	at org.apache.commons.lang3.Validate.notNull(Validate.java:222) ~[commons-lang3-3.2.1.jar:3.2.1]
[16:27:45 INFO]: Client> 	at org.apache.commons.lang3.Validate.notNull(Validate.java:203) ~[commons-lang3-3.2.1.jar:3.2.1]
[16:27:45 INFO]: Client> 	at up.a(SourceFile:39) ~[14w20b.jar:?]
[16:27:45 INFO]: Client> 	at up.a(SourceFile:212) ~[14w20b.jar:?]
[16:27:45 INFO]: Client> 	at uy.a(SourceFile:116) ~[14w20b.jar:?]
[16:27:45 INFO]: Client> 	at ty.f(SourceFile:1151) ~[14w20b.jar:?]
[16:27:45 INFO]: Client> 	... 21 more
[16:27:47 INFO]: Client> [16:27:47] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 3620ms behind, skipping 72 tick(s)
[16:27:48 INFO]: Client> [16:27:48] [Server thread/INFO]: Saving and pausing game...
[16:27:48 INFO]: Client> [16:27:48] [Server thread/INFO]: Saving chunks for level 'Waking Up'/Overworld
[16:27:48 INFO]: Client> [16:27:48] [Server thread/INFO]: Saving chunks for level 'Waking Up'/Nether
[16:27:48 INFO]: Client> [16:27:48] [Server thread/INFO]: Saving chunks for level 'Waking Up'/The End
[16:28:06 INFO]: Client> [16:28:06] [Server thread/INFO]: NekoJonez fell out of the world
[16:28:06 INFO]: Client> [16:28:06] [Client thread/INFO]: [CHAT] NekoJonez fell out of the world
[16:28:09 INFO]: Client> [16:28:09] [pool-2-thread-1/ERROR]: Signature is missing from textures payload
[16:28:35 INFO]: Client> [16:28:35] [Server thread/INFO]: Saving and pausing game...
[16:28:35 INFO]: Client> [16:28:35] [Server thread/INFO]: Saving chunks for level 'Waking Up'/Overworld
[16:28:35 INFO]: Client> [16:28:35] [Server thread/INFO]: Saving chunks for level 'Waking Up'/Nether
[16:28:35 INFO]: Client> [16:28:35] [Server thread/INFO]: Saving chunks for level 'Waking Up'/The End
[16:28:35 INFO]: Client> [16:28:35] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 25989ms behind, skipping 519 tick(s)

So, similar things like this happen when I try to load eg a Vechs map or several other custom maps.