"open_url" crash command (Tellraw)

/tellraw @a {"text":"Saved screenshot as","color":white,"extra":[{"text":" 2014_4_1_16.40.35.png","color":white,underlined:true,"clickEvent":{"action":"open_url","value":""}}]}

---- Minecraft Crash Report ----
// Oh - I know what I did wrong!

Time: 01.04.14 17:00
Description: Updating screen events

java.lang.NullPointerException: Updating screen events
	at bbj.a(SourceFile:155)
	at bcl.d(SourceFile:232)
	at bbj.d(SourceFile:127)
	at bcl.k(SourceFile:211)
	at azi.p(SourceFile:1308)
	at azi.ah(SourceFile:760)
	at azi.f(SourceFile:711)
	at net.minecraft.client.main.Main.main(SourceFile:152)


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

-- Head --
Stacktrace:
	at bbj.a(SourceFile:155)
	at bcl.d(SourceFile:232)
	at bbj.d(SourceFile:127)
	at bcl.k(SourceFile:211)

-- Affected screen --
Details:
	Screen name: bbj

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bkf['damien_say_hallo'/58, l='MpServer', x=257,50, y=6,62, z=-364,20]]
	Chunk stats: MultiplayerChunkCache: 289, 289
	Level seed: 0
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: World: (229,14,-366), Chunk: (at 5,0,2 in 14,-23; contains blocks 224,0,-368 to 239,255,-353), Region: (0,-1; contains chunks 0,-32 to 31,-1, blocks 0,0,-512 to 511,255,-1)
	Level time: 252580 game time, 1101 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: 20 total; [rs['Painting'/9, l='MpServer', x=244,50, y=8,50, z=-385,06], rs['Painting'/10, l='MpServer', x=241,50, y=8,50, z=-385,06], rs['Painting'/2, l='MpServer', x=247,06, y=8,50, z=-388,00], rs['Painting'/3, l='MpServer', x=240,06, y=8,50, z=-389,50], rs['Painting'/4, l='MpServer', x=240,06, y=8,50, z=-386,50], rs['Painting'/5, l='MpServer', x=241,50, y=8,50, z=-390,94], rs['Painting'/5, l='MpServer', x=241,50, y=8,50, z=-390,94], rs['Painting'/6, l='MpServer', x=244,50, y=8,50, z=-390,94], rs['Painting'/7, l='MpServer', x=245,94, y=8,50, z=-389,50], rs['Painting'/6, l='MpServer', x=244,50, y=8,50, z=-390,94], rs['Painting'/8, l='MpServer', x=245,94, y=8,50, z=-386,50], rs['Painting'/7, l='MpServer', x=245,94, y=8,50, z=-389,50], rs['Painting'/8, l='MpServer', x=245,94, y=8,50, z=-386,50], rs['Painting'/9, l='MpServer', x=244,50, y=8,50, z=-385,06], rs['Painting'/10, l='MpServer', x=241,50, y=8,50, z=-385,06], wd['entity.MinecartChest.name'/15, l='MpServer', x=285,50, y=5,50, z=-361,50], bkf['damien_say_hallo'/58, l='MpServer', x=257,50, y=6,62, z=-364,20], rs['Painting'/4, l='MpServer', x=240,06, y=8,50, z=-386,50], rs['Painting'/3, l='MpServer', x=240,06, y=8,50, z=-389,50], rs['Painting'/2, l='MpServer', x=247,06, y=8,50, z=-388,00]]
	Retry entities: 0 total; []
	Server brand: vanilla
	Server type: Integrated singleplayer server
Stacktrace:
	at bka.a(SourceFile:289)
	at azi.b(SourceFile:1952)
	at azi.f(SourceFile:720)
	at net.minecraft.client.main.Main.main(SourceFile:152)

-- System Details --
Details:
	Minecraft Version: 1.7.4
	Operating System: Windows 7 (x86) version 6.1
	Java Version: 1.7.0_51, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 50270752 bytes (47 MB) / 138448896 bytes (132 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 22 (1232 bytes; 0 MB) allocated, 2 (112 bytes; 0 MB) used
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Launched Version: 1.7.4
	LWJGL: 2.9.1
	OpenGL: AMD Radeon HD 6310 Graphics GL version 4.0.10318 Compatibility Profile Context, ATI Technologies Inc.
	GL Caps: Using GL 1.3 multitexturing.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Anisotropic filtering is supported and maximum anisotropy is 16.
Shaders are available because OpenGL 2.1 is supported.

	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Packs: []
	Current Language: English (UK)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 75 (4200 bytes; 0 MB) allocated, 20 (1120 bytes; 0 MB) used
	Anisotropic Filtering: Off (1)