Bug 904628 - Ensure focused element is not null when calling FormAssistant.updateSelection(). r=fabrice

b2g/chrome/content/forms.js

@@ -667,6 +667,9 @@ let FormAssistant = {
 
   // Notify when the selection range changes
   updateSelection: function fa_updateSelection() {
+    if (!this.focusedElement) {
+      return;
+    }
     let selectionInfo = this.getSelectionInfo();
     if (selectionInfo.changed) {
       sendAsyncMessage("Forms:SelectionChange", this.getSelectionInfo());