Bug 1230911 - modified asseert in order to prevent null pointer dereference. r=roc

gfx/layers/client/TextureClient.cpp

@@ -820,7 +820,8 @@ TextureClient::CreateForRawBufferAccess(ISurfaceAllocator* aAllocator,
                                         TextureFlags aTextureFlags,
                                         TextureAllocationFlags aAllocFlags)
 {
-  MOZ_ASSERT(aAllocator->IPCOpen());
+  // also test the validity of aAllocator
+  MOZ_ASSERT(aAllocator && aAllocator->IPCOpen());
   if (!aAllocator || !aAllocator->IPCOpen()) {
     return nullptr;
   }