Changed ZoomOut control to inherit from OpenLayers.Control.Button.

lib/OpenLayers/Control/ZoomOut.js

@@ -4,7 +4,7 @@
  * full text of the license. */
 
 /**
- * @requires OpenLayers/Control.js
+ * @requires OpenLayers/Control/Button.js
  */
 
 /**
@@ -14,21 +14,15 @@
  * Inherits from:
  *  - <OpenLayers.Control>
  */
-OpenLayers.Control.ZoomOut = OpenLayers.Class(OpenLayers.Control, {
+OpenLayers.Control.ZoomOut = OpenLayers.Class(OpenLayers.Control.Button, {
 
-    /**
-     * Property: type
-     * {String} The type of <OpenLayers.Control> -- When added to a 
-     *     <Control.Panel>, 'type' is used by the panel to determine how to 
-     *     handle our events.
-     */
-    type: OpenLayers.Control.TYPE_BUTTON,
-    
     /**
      * Method: trigger
      */
     trigger: function(){
-        this.map.zoomOut();
+        if (this.map) {
+            this.map.zoomOut();
+        }
     },
 
     CLASS_NAME: "OpenLayers.Control.ZoomOut"