Bug 1609224 - Don't use PlacesUtils if it's not defined. r=jdescottes

Differential Revision: https://phabricator.services.mozilla.com/D60266

--HG--
extra : moz-landing-system : lando

devtools/server/actors/targets/frame-proxy.js

@@ -22,6 +22,7 @@ loader.lazyImporter(
   "PlacesUtils",
   "resource://gre/modules/PlacesUtils.jsm"
 );
+const { AppConstants } = require("resource://gre/modules/AppConstants.jsm");
 
 /**
  * Creates a target actor proxy for handling requests to a single browser frame.
@@ -99,6 +100,11 @@ exports.FrameTargetActorProxy = protocol.ActorClassWithSpec(proxySpec, {
   },
 
   async getFaviconData() {
+    if (!AppConstants.MOZ_PLACES) {
+      // PlacesUtils is not supported
+      return null;
+    }
+
     try {
       const { data } = await PlacesUtils.promiseFaviconData(this._form.url);
       return data;