Bug 1133645 - Check size of audio_specific_config before use. r=snorp

dom/media/fmp4/android/AndroidDecoderModule.cpp

@@ -205,7 +205,7 @@ public:
     jni::Object::LocalRef buffer(env);
     NS_ENSURE_SUCCESS_VOID(aFormat->GetByteBuffer(NS_LITERAL_STRING("csd-0"), &buffer));
 
-    if (!buffer) {
+    if (!buffer && aConfig.audio_specific_config->Length() >= 2) {
       csd0[0] = (*aConfig.audio_specific_config)[0];
       csd0[1] = (*aConfig.audio_specific_config)[1];