fix for #859 - make default return from OpenLayers.Util.Try() explicitly null. Also add tests and documentations

git-svn-id: http://svn.openlayers.org/trunk/openlayers@3816 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Util.js

@@ -543,10 +543,21 @@ OpenLayers.Util.getImagesLocation = function() {
 
 /** 
  * Function: Try
+ * Execute functions until one of them doesn't throw an error. 
+ *     Capitalized because "try" is a reserved word in JavaScript.
+ *     Taken directly from OpenLayers.Util.Try()
  * 
+ * Parameters:
+ * [*] - {Function} Any number of parameters may be passed to Try()
+ *    It will attempt to execute each of them until one of them 
+ *    successfully executes. 
+ *    If none executes successfully, returns null.
+ * 
+ * Return:
+ * {*} The value returned by the first successfully executed function.
  */
 OpenLayers.Util.Try = function() {
-    var returnValue;
+    var returnValue = null;
 
     for (var i = 0; i < arguments.length; i++) {
       var lambda = arguments[i];