remoteSearch: We do not need a fallback for createIcon

Remote providers no longer have access to a grid layout, where an icon is
a requirement. If they don't specify an icon, don't create one.

https://bugzilla.gnome.org/show_bug.cgi?id=681797

js/ui/remoteSearch.js

@@ -196,9 +196,7 @@ const RemoteSearchProvider = new Lang.Class({
                                               width, height, rowStride, size);
         }
 
-        // Ugh, but we want to fall back to something ...
-        return new St.Icon({ icon_name: 'text-x-generic',
-                             icon_size: size });
+        return null;
     },
 
     _getResultsFinished: function(results, error) {