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

--HG--
extra : rebase_source : 04bbec02d594e0006ed127005a3cc653cb5e195f

gfx/layers/client/TextureClient.cpp

@@ -693,7 +693,8 @@ TextureClient::CreateForDrawing(CompositableForwarder* 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;
   }