Bug 1833351 - Handle invalid URI to nsIconChannel gracefully. r=jld

Differential Revision: https://phabricator.services.mozilla.com/D178158

image/decoders/icon/gtk/nsIconChannel.cpp

@@ -294,6 +294,10 @@ nsresult nsIconChannel::GetIcon(nsIURI* aURI, ByteBuf* aDataOut) {
   nsCOMPtr<nsIMozIconURI> iconURI = do_QueryInterface(aURI);
   NS_ASSERTION(iconURI, "URI is not an nsIMozIconURI");
 
+  if (!iconURI) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
   if (gfxPlatform::IsHeadless()) {
     return NS_ERROR_NOT_AVAILABLE;
   }