1. I enter in my world
2. I put a tnt
3. On the top of the tnt, I put a traped chest
4. I open the chest so the tnt explotes.
5. I get this error:
Minecraft has crashed!
----------------------

Minecraft has stopped running because it encountered a problem; Ticking memory connection

A full error report has been saved to C:\Users\guillermo\AppData\Roaming\.minecraft\crash-reports\crash-2013-01-04_10.17.26-server.txt - Please include a copy of that file (Not this screen!) if you report this crash to anyone; without it, they will not be able to help fix the crash

— BEGIN ERROR REPORT f213c088 --------
Full report at:
C:\Users\guillermo\AppData\Roaming\.minecraft\crash-reports\crash-2013-01-04_10.17.26-server.txt
Please show that file to Mojang, NOT just this screen!

Generated 4/01/13 10:17

– System Details –
Details:
Minecraft Version: 13w01a
Operating System: Windows 7 (amd64) version 6.1
Java Version: 1.7.0_07, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 60880696 bytes (58 MB) / 872218624 bytes (831 MB) up to 954466304 bytes (910 MB)
JVM Flags: 2 total; -Xms512m -Xmx1024m
AABB Pool Size: 4714 (263984 bytes; 0 MB) allocated, 2009 (112504 bytes; 0 MB) used
Suspicious classes: No suspicious classes found.
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
Profiler Position: N/A (disabled)
Vec3 Pool Size: 716 (40096 bytes; 0 MB) allocated, 716 (40096 bytes; 0 MB) used
Player Count: 1 / 8; [iq['guillermolmr'/2044606, l='1.4', x=1117,49, y=55,97, z=1033,14]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.

java.lang.NullPointerException
at anu.f(SourceFile:247)
at rx.b(SourceFile:68)
at iq.k(SourceFile:482)
at iq.i(SourceFile:467)
at qx.j_(SourceFile:204)
at iq.g(SourceFile:175)
at iv.a(SourceFile:199)
at eb.a(SourceFile:136)
at cf.b(SourceFile:55)
at iv.d(SourceFile:57)
at iw.b(SourceFile:39)
at beq.b(SourceFile:84)
at net.minecraft.server.MinecraftServer.r(SourceFile:762)
at net.minecraft.server.MinecraftServer.q(SourceFile:679)
at ben.q(SourceFile:117)
at net.minecraft.server.MinecraftServer.run(SourceFile:613)
at fy.run(SourceFile:849)
— END ERROR REPORT 27c4a97c ----------