Bug 700553 - test_add_remove_dictionaries.xul silently fails with uncaught JS exception; r=ehsan

extensions/spellcheck/tests/chrome/test_add_remove_dictionaries.xul

@@ -12,7 +12,6 @@
   <script type="application/javascript">
   <![CDATA[
 SimpleTest.waitForExplicitFinish();
-SimpleTest.ignoreAllUncaughtExceptions();
 
 function getMisspelledWords(editor) {
   return editor.selectionController.getSelection(Components.interfaces.nsISelectionController.SELECTION_SPELLCHECK).toString();
@@ -36,7 +35,9 @@ function setCurrentDictionary(editor, dictionary) {
 }
 
 function RunTest() {
-  var editor = document.getElementById('textbox').editor;
+  var textbox = document.getElementById('textbox');
+  textbox.focus();
+  var editor = textbox.editor;
 
   var dir = Components.classes["@mozilla.org/file/directory_service;1"].
             getService(Components.interfaces.nsIProperties).