make sure to return NS_OK from Init()

gfx/src/xlib/nsRenderingContextXlib.cpp

@@ -116,6 +116,7 @@ nsRenderingContextXlib::Init(nsIDeviceContext* aContext, nsDrawingSurface aSurfa
 nsresult nsRenderingContextXlib::CommonInit(void)
 {
   // put common stuff in here.
+  return NS_OK;
 }
 
 NS_IMETHODIMP