So me and my friend were screwing around with the 1.7.1 server, and we started using tellraw. Then I tried to mess with him by giving him a null message. When I did /tellraw @a null it crashed both of our clients.
STEPS TO REPRODUCE:
Go on the server (1.7.1)
Op yourself
Do /tellraw @a null
Boom
Crash log:
---- Minecraft Crash Report ----
// Why is it breaking :(
Time: 10/23/13 4:21 PM
Description: Unexpected error
java.lang.NullPointerException: Unexpected error
at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:192)
at com.google.common.collect.Lists.newArrayList(Lists.java:126)
at ban.a(SourceFile:144)
at ban.a(SourceFile:123)
at ban.a(SourceFile:119)
at biu.a(SourceFile:456)
at fz.a(SourceFile:38)
at fz.a(SourceFile:9)
at ef.a(SourceFile:143)
at bix.e(SourceFile:212)
at azc.o(SourceFile:1281)
at azc.ad(SourceFile:753)
at azc.e(SourceFile:704)
at net.minecraft.client.main.Main.main(SourceFile:103)
A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------
-- Head --
Stacktrace:
at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:192)
at com.google.common.collect.Lists.newArrayList(Lists.java:126)
at ban.a(SourceFile:144)
at ban.a(SourceFile:123)
at ban.a(SourceFile:119)
at biu.a(SourceFile:456)
at fz.a(SourceFile:38)
at fz.a(SourceFile:9)
at ef.a(SourceFile:143)
at bix.e(SourceFile:212)
-- Affected level --
Details:
Level name: MpServer
All players: 1 total; [bjd['etherock'/4946, l='MpServer', x=-6.70, y=62.62, z=194.23]]
Chunk stats: MultiplayerChunkCache: 49, 49
Level seed: 0
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: World: (18,64,248), Chunk: (at 2,4,8 in 1,15; contains blocks 16,0,240 to 31,255,255), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 3799188 game time, 3799188 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: 9 total; [vv['item.tile.sapling.oak'/2869, l='MpServer', x=13.72, y=74.13, z=205.88], bjd['etherock'/4946, l='MpServer', x=-6.70, y=62.62, z=194.23], vv['item.tile.sapling.oak'/2375, l='MpServer', x=5.97, y=68.13, z=201.88], vv['item.item.porkchopCooked'/4945, l='MpServer', x=12.13, y=67.13, z=199.88], up['Bat'/4971, l='MpServer', x=-25.81, y=46.99, z=201.57], up['Bat'/4970, l='MpServer', x=-27.02, y=44.53, z=203.49], vv['item.tile.torch'/4943, l='MpServer', x=7.75, y=73.13, z=196.56], vv['item.tile.sapling.oak'/2514, l='MpServer', x=8.53, y=81.13, z=205.56], vv['item.tile.sapling.oak'/4201, l='MpServer', x=10.09, y=80.13, z=204.00]]
Retry entities: 0 total; []
Server brand: vanilla
Server type: Non-integrated multiplayer server
Stacktrace:
at biy.a(SourceFile:284)
at azc.b(SourceFile:1949)
at azc.e(SourceFile:718)
at net.minecraft.client.main.Main.main(SourceFile:103)
-- System Details --
Details:
Minecraft Version: 1.7.1
Operating System: Windows 7 (amd64) version 6.1
Java Version: 1.7.0_40, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 374623592 bytes (357 MB) / 609222656 bytes (581 MB) up to 954728448 bytes (910 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
AABB Pool Size: 7741 (433496 bytes; 0 MB) allocated, 2 (112 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
Launched Version: 1.7.1
LWJGL: 2.9.0
OpenGL: GeForce 210/PCIe/SSE2 GL version 3.3.0, NVIDIA Corporation
Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Packs: []
Current Language: English (US)
Profiler Position: N/A (disabled)
Vec3 Pool Size: 1943 (108808 bytes; 0 MB) allocated, 20 (1120 bytes; 0 MB) used
Anisotropic Filtering: On (4)
Server log when performing
tellraw @a null
[16:29:04] [Server thread/INFO]: adam223344 lost connection: TranslatableCompone
nt{key='disconnect.genericReason', args=[Internal Exception: java.io.IOException
: An existing connection was forcibly closed by the remote host], siblings=[], s
tyle=Style{hasParent=false, color=null, bold=null, italic=null, underlined=null,
obfuscated=null, clickEvent=null, hoverEvent=null}}
[16:29:04] [Server thread/INFO]: adam223344 left the game
[16:29:19] [User Authenticator #3/INFO]: UUID of player adam223344 is 7f5301e567
42427cafe1e0df2fd9f8cb
[16:29:19] [Server thread/INFO]: adam223344[/82.5.77.226:53819] logged in with e
ntity id 661 at (-49.52345296150794, 77.24918707874468, 374.2445096075345)
[16:29:19] [Server thread/INFO]: adam223344 joined the game
Comments
Oh, thanks for telling me. 😉
Will I be getting an assignee or someone in mojang to review the issue?
Still in 10c
Happens in 1.7.6-pre2 as well
Fixed in 14w25b, "null" makes the game output nothing so it never causes a crash

Confirmed for
1.8.4 Minecraft still isn't testing if the value is
null
before performing the command (but doesn't crash anymore):
/tellraw @p null
[23:59:39] [Client thread/FATAL]: Error executing task
java.util.concurrent.ExecutionException: java.lang.NullPointerException
at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:1.8.0_25]
at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[?:1.8.0_25]
at g.a(SourceFile:61) [1.8.4.jar:?]
at ave.av(SourceFile:880) [1.8.4.jar:?]
at ave.a(SourceFile:325) [1.8.4.jar:?]
at net.minecraft.client.main.Main.main(SourceFile:124) [1.8.4.jar:?]
Caused by: java.lang.NullPointerException
at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:213) ~[guava-17.0.jar:?]
at com.google.common.collect.Lists.newArrayList(Lists.java:127) ~[guava-17.0.jar:?]
at avu.a(SourceFile:25) ~[1.8.4.jar:?]
at avt.a(SourceFile:139) ~[1.8.4.jar:?]
at avt.a(SourceFile:129) ~[1.8.4.jar:?]
at avt.a(SourceFile:125) ~[1.8.4.jar:?]
at bcy.a(SourceFile:527) ~[1.8.4.jar:?]
at fy.a(SourceFile:44) ~[1.8.4.jar:?]
at fy.a(SourceFile:9) ~[1.8.4.jar:?]
at fh$1.run(SourceFile:13) ~[1.8.4.jar:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_25]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[?:1.8.0_25]
at g.a(SourceFile:60) ~[1.8.4.jar:?]
... 3 more
{code:title=/tellraw @p {text:null}}
[00:00:44] [Server thread/WARN]: Couldn't process command: 'tellraw @p {text:null}'

still 1.7.9
This got fixed in 1.8, outdated versions are not supported.
This is not a duplicate of anything hopper related, so why is anything hopper related showing up on my duplicates section. Seriously? You are saying this is hopper related? It's nothing near hoppers!