Hopper: java.lang.UnsupportedOperationException: JsonNull

java.lang.UnsupportedOperationException: JsonNull
	at com.google.gson.JsonElement.getAsString(JsonElement.java:185)
	at boj.a(SourceFile:90)
	at boj.c(SourceFile:113)
	at boa.b(SourceFile:132)
	at bbg.a(SourceFile:73)
	at bbg.a(SourceFile:106)
	at ayr.n(SourceFile:154)
	at ayr.m(SourceFile:115)

---- Minecraft Crash Report ----
// Everything's going to plan. No, really, that was supposed to happen.

Time: 9/5/13 2:08 PM
Description: Updating screen events

java.lang.UnsupportedOperationException: JsonNull
	at com.google.gson.JsonElement.getAsString(JsonElement.java:185)
	at boj.a(SourceFile:90)
	at boj.c(SourceFile:113)
	at boa.b(SourceFile:132)
	at bbg.a(SourceFile:73)
	at bbg.a(SourceFile:106)
	at ayr.n(SourceFile:154)
	at ayr.m(SourceFile:115)
	at avx.m(SourceFile:1202)
	at avx.V(SourceFile:686)
	at avx.e(SourceFile:642)
	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.gson.JsonElement.getAsString(JsonElement.java:185)
	at boj.a(SourceFile:90)
	at boj.c(SourceFile:113)
	at boa.b(SourceFile:132)
	at bbg.a(SourceFile:73)
	at bbg.a(SourceFile:106)
	at ayr.n(SourceFile:154)
	at ayr.m(SourceFile:115)

-- Affected screen --
Details:
	Screen name: bbg
Stacktrace:
	at avx.m(SourceFile:1202)
	at avx.V(SourceFile:686)
	at avx.e(SourceFile:642)
	at net.minecraft.client.main.Main.main(SourceFile:103)

-- System Details --
Details:
	Minecraft Version: 13w36a
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.7.0_21, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 93099384 bytes (88 MB) / 282066944 bytes (269 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
	AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	Suspicious classes: [com.ibm.icu.impl.UBiDiProps, Authenticate, ICUData, ...], [com.ibm.icu.lang.ECharacterCategory, ECharacterDirection, UCharacter], [com.ibm.icu.text.ArabicShapingException, Bidi, ImpTabPair, ...], [com.ibm.icu.util.ValueIterator, RangeValueIterator], [gnu.trove.TIntCollection], [gnu.trove.impl.HashFunctions, PrimeFinder], [gnu.trove.impl.hash.THash, TPrimitiveHash, TIntIntHash], [gnu.trove.iterator.TIterator, TAdvancingIterator, TIntIntIterator], [gnu.trove.map.TIntIntMap], [gnu.trove.map.hash.TIntIntHashMap], [gnu.trove.procedure.TIntIntProcedure], [gnu.trove.set.TIntSet]
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Launched Version: 13w36a
	LWJGL: 2.9.0
	OpenGL: GeForce GTX 260/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: ~~ERROR~~ NullPointerException: null