I just played Minecraft in my Creative Word, with no generated blocks, i just builded islands. and then it crached with:

Connection lost
Server closed

Serious?
...and then i was in the Multiplayer screen.

And here is a Debug Crash Report after loading the world again:

---- Minecraft Crash Report ----
// Quite honestly, I wouldn't worry myself about that.

Time: 23.07.14 19:58
Description: Manually triggered debug crash

java.lang.Throwable
at brk.r(SourceFile:1569)
at brk.ar(SourceFile:875)
at brk.a(SourceFile:310)
at net.minecraft.client.main.Main.main(SourceFile:120)

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

– Head –
Stacktrace:
at ccu.a(SourceFile:308)

– Affected level –
Details:
Level name: MpServer
All players: 1 total; [cgv['timmy14085'/626, l='MpServer', x=-129,06, y=113,00, z=-75,53]]
Chunk stats: MultiplayerChunkCache: 289, 289
Level seed: 0
Level generator: ID 01 - flat, ver 0. Features enabled: false
Level generator options:
Level spawn location: 15,00,110,00,-45,00 - World: (15,110,-45), Chunk: (at 15,6,3 in 0,-3; contains blocks 0,0,-48 to 15,255,-33), Region: (0,-1; contains chunks 0,-32 to 31,-1, blocks 0,0,-512 to 511,255,-1)
Level time: 4966796 game time, 6000 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: Game mode: creative (ID 1). Hardcore: false. Cheats: false
Forced entities: 37 total; [abi['Huhn'/0, l='MpServer', x=-137,81, y=115,50, z=-101,81], abi['Huhn'/1, l='MpServer', x=-137,81, y=115,50, z=-101,22], abi['Huhn'/2, l='MpServer', x=-137,81, y=115,50, z=-101,81], abi['Huhn'/3, l='MpServer', x=-137,81, y=115,50, z=-101,22], abi['Huhn'/4, l='MpServer', x=-137,81, y=115,50, z=-101,22], abi['Huhn'/5, l='MpServer', x=-137,81, y=115,50, z=-101,81], abi['Huhn'/6, l='MpServer', x=-137,22, y=115,50, z=-101,81], abi['Huhn'/7, l='MpServer', x=-137,81, y=115,50, z=-101,22], abi['Huhn'/8, l='MpServer', x=-137,22, y=115,50, z=-101,81], abi['Huhn'/9, l='MpServer', x=-137,81, y=115,50, z=-101,22], abi['Huhn'/10, l='MpServer', x=-137,22, y=115,50, z=-101,81], abi['Huhn'/11, l='MpServer', x=-137,81, y=115,50, z=-101,22], abi['Huhn'/12, l='MpServer', x=-137,22, y=115,50, z=-101,81], abi['Huhn'/13, l='MpServer', x=-137,81, y=115,50, z=-101,22], abi['Huhn'/14, l='MpServer', x=-137,22, y=115,50, z=-101,81], abi['Huhn'/15, l='MpServer', x=-137,81, y=115,50, z=-101,81], abi['Huhn'/16, l='MpServer', x=-137,81, y=115,50, z=-101,22], abi['Huhn'/17, l='MpServer', x=-137,22, y=115,50, z=-101,81], abi['Huhn'/18, l='MpServer', x=-137,81, y=115,50, z=-101,22], abi['Huhn'/19, l='MpServer', x=-137,22, y=115,50, z=-101,81], abi['Huhn'/20, l='MpServer', x=-137,81, y=115,50, z=-101,22], abi['Huhn'/21, l='MpServer', x=-137,81, y=115,50, z=-101,22], abi['Huhn'/22, l='MpServer', x=-137,22, y=115,50, z=-101,81], abi['Huhn'/23, l='MpServer', x=-137,81, y=115,50, z=-101,22], abi['Huhn'/24, l='MpServer', x=-137,22, y=115,50, z=-101,81], abi['Huhn'/25, l='MpServer', x=-137,81, y=115,50, z=-101,22], abi['Huhn'/26, l='MpServer', x=-137,22, y=115,50, z=-101,81], abi['Huhn'/27, l='MpServer', x=-137,81, y=115,50, z=-101,22], abi['Huhn'/28, l='MpServer', x=-137,22, y=115,50, z=-101,81], abi['Huhn'/29, l='MpServer', x=-138,91, y=113,50, z=-102,91], abi['Huhn'/30, l='MpServer', x=-138,59, y=113,50, z=-102,38], abi['Huhn'/31, l='MpServer', x=-138,13, y=113,50, z=-102,13], abi['Huhn'/32, l='MpServer', x=-138,13, y=113,50, z=-102,91], adm['entity.MinecartRideable.name'/33, l='MpServer', x=-139,88, y=113,00, z=-75,50], abr['Schwein'/34, l='MpServer', x=-119,19, y=113,00, z=-65,72], adk['entity.MinecartFurnace.name'/35, l='MpServer', x=-127,16, y=113,00, z=-75,50], cgv['timmy14085'/626, l='MpServer', x=-129,06, y=113,00, z=-75,53]]
Retry entities: 0 total; []
Server brand: vanilla
Server type: Integrated singleplayer server
Stacktrace:
at ccu.a(SourceFile:308)
at brk.b(SourceFile:2262)
at brk.a(SourceFile:319)
at net.minecraft.client.main.Main.main(SourceFile:120)

– System Details –
Details:
Minecraft Version: 14w30b
Operating System: Windows 8 (amd64) version 6.2
Java Version: 1.8.0_05, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 92007808 bytes (87 MB) / 266862592 bytes (254 MB) up to 2863661056 bytes (2731 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx3G
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
Launched Version: 14w30b
LWJGL: 2.9.1
OpenGL: Intel(R) HD Graphics 4000 GL version 4.0.0 - Build 10.18.10.3412, Intel
GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.

Using VBOs: Yes
Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Packs: []
Current Language: Deutsch (Deutschland)
Profiler Position: N/A (disabled)