wined3d: Make sure volumes have memory allocated.

dlls/wined3d/volume.c

@@ -141,6 +141,10 @@ static HRESULT WINAPI IWineD3DVolumeImpl_LockBox(IWineD3DVolume *iface, WINED3DL
     IWineD3DVolumeImpl *This = (IWineD3DVolumeImpl *)iface;
     FIXME("(%p) : pBox=%p stub\n", This, pBox);
 
+    if(!This->resource.allocatedMemory) {
+        This->resource.allocatedMemory = HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, This->resource.size);
+    }
+
     /* fixme: should we really lock as such? */
     TRACE("(%p) : box=%p, output pbox=%p, allMem=%p\n", This, pBox, pLockedVolume, This->resource.allocatedMemory);