Hopper: java.lang.UnsupportedOperationException: JsonNull

java.lang.UnsupportedOperationException: JsonNull
	at com.google.gson.JsonElement.getAsString(JsonElement.java:185)
	at bpx.a(SourceFile:90)
	at bpx.c(SourceFile:113)
	at bpo.b(SourceFile:132)
	at bcg.a(SourceFile:76)
	at azr.a(SourceFile:172)
	at bcg.a(SourceFile:115)
	at azr.d(SourceFile:236)
	at azr.n(SourceFile:211)

---- Minecraft Crash Report ----
// Uh... Did I do that?

Time: 9/27/13 3:22 PM
Description: Updating screen events

java.lang.UnsupportedOperationException: JsonNull
	at com.google.gson.JsonElement.getAsString(JsonElement.java:185)
	at bpx.a(SourceFile:90)
	at bpx.c(SourceFile:113)
	at bpo.b(SourceFile:132)
	at bcg.a(SourceFile:76)
	at azr.a(SourceFile:172)
	at bcg.a(SourceFile:115)
	at azr.d(SourceFile:236)
	at azr.n(SourceFile:211)
	at awq.o(SourceFile:1281)
	at awq.aa(SourceFile:753)
	at awq.e(SourceFile:704)
	at net.minecraft.client.main.Main.main(SourceFile:104)


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

-- Head --
Stacktrace:
	at com.google.gson.JsonElement.getAsString(JsonElement.java:185)
	at bpx.a(SourceFile:90)
	at bpx.c(SourceFile:113)
	at bpo.b(SourceFile:132)
	at bcg.a(SourceFile:76)
	at azr.a(SourceFile:172)
	at bcg.a(SourceFile:115)
	at azr.d(SourceFile:236)
	at azr.n(SourceFile:211)

-- Affected screen --
Details:
	Screen name: bcg
Stacktrace:
	at awq.o(SourceFile:1281)
	at awq.aa(SourceFile:753)
	at awq.e(SourceFile:704)
	at net.minecraft.client.main.Main.main(SourceFile:104)

-- System Details --
Details:
	Minecraft Version: 13w39b
	Operating System: Windows 8 (x86) version 6.2
	Java Version: 1.7.0_40, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 21039224 bytes (20 MB) / 71258112 bytes (67 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: 0, tallocated: 0
	Launched Version: 13w39b
	LWJGL: 2.9.0
	OpenGL: Intel(R) HD Graphics 4000 GL version 4.0.0 - Build 9.17.10.2849, Intel
	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: ~~ERROR~~ NullPointerException: null