Hopper: java.lang.NullPointerException: Updating screen events

java.lang.NullPointerException: Updating screen events
	at bbu.a(SourceFile:63)
	at bbo.a(SourceFile:42)
	at bco.a(SourceFile:172)
	at bco.d(SourceFile:232)
	at bco.k(SourceFile:211)

---- Minecraft Crash Report ----
// Who set us up the TNT?

Time: 26/02/14 10:39
Description: Updating screen events

java.lang.NullPointerException: Updating screen events
	at bbu.a(SourceFile:63)
	at bbo.a(SourceFile:42)
	at bco.a(SourceFile:172)
	at bco.d(SourceFile:232)
	at bco.k(SourceFile:211)
	at azl.p(SourceFile:1303)
	at azl.ah(SourceFile:757)
	at azl.f(SourceFile:711)
	at net.minecraft.client.main.Main.main(SourceFile:148)


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

-- Head --
Stacktrace:
	at bbu.a(SourceFile:63)
	at bbo.a(SourceFile:42)
	at bco.a(SourceFile:172)
	at bco.d(SourceFile:232)
	at bco.k(SourceFile:211)

-- Affected screen --
Details:
	Screen name: bcw
Stacktrace:
	at azl.p(SourceFile:1303)
	at azl.ah(SourceFile:757)
	at azl.f(SourceFile:711)
	at net.minecraft.client.main.Main.main(SourceFile:148)

-- System Details --
Details:
	Minecraft Version: 1.7.5
	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: 158825392 bytes (151 MB) / 226312192 bytes (215 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
	Launched Version: 1.7.5
	LWJGL: 2.9.1
	OpenGL: ATI Radeon HD 3200 Graphics   GL version 2.1.8794, ATI Technologies Inc.
	GL Caps: Using GL 1.3 multitexturing.
Using framebuffer objects because ARB_framebuffer_object 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: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	Anisotropic Filtering: Off (1)