Fix buttons on about:support when not building updater.

toolkit/content/aboutSupport.js

@@ -643,10 +643,12 @@ function safeModeRestart() {
  * Set up event listeners for buttons.
  */
 function setupEventListeners(){
+#ifdef MOZ_UPDATER
   $("show-update-history-button").addEventListener("click", function (event) {
     var prompter = Cc["@mozilla.org/updates/update-prompt;1"].createInstance(Ci.nsIUpdatePrompt);
       prompter.showUpdateHistory(window);
   });
+#endif
   $("reset-box-button").addEventListener("click", function (event){
     ResetProfile.openConfirmationDialog(window);
   });