Stop the settings modal from being open multiple consecutive times.

ardublockly/ardublockly_design.js

@@ -307,14 +307,21 @@ Ardublockly.openNotConnectedModal = function() {
   });
 };
 
+/** Tracks if the settings modal is currently opened. */
+Ardublockly.settingsOpen = false;
+
 /** Opens the modal that displays the Settings. */
 Ardublockly.openSettingsModal = function() {
+  if (!Ardublockly.settingsOpen) {
+    Ardublockly.settingsOpen = true;
     $('#settings_dialog').openModal({
       dismissible: true,
       opacity: .5,
       in_duration: 200,
-    out_duration: 250
+      out_duration: 250,
+      complete: function() { Ardublockly.settingsOpen = false; } 
     });
+  }
 };
 
 /**