cannot destroy a map with panels, r=fredj (closes #2864)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@10810 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Control.js

@@ -343,7 +343,10 @@ OpenLayers.Control = OpenLayers.Class({
                     this.displayClass.replace(/ /g, "") + "Active"
                 );
             }
-            this.events.triggerEvent("deactivate");
+            // deal with the case where the control is destroyed
+            if(this.events) {
+                this.events.triggerEvent("deactivate");
+            }
             return true;
         }
         return false;