improve whitespace detection

select2.js

@@ -476,7 +476,7 @@
 
             installKeyUpChangeEvent(search);
             search.bind("keyup-change", this.bind(this.updateResults));
-            search.bind("focus", function () { search.addClass("select2-focused"); search.val(""); });
+            search.bind("focus", function () { search.addClass("select2-focused"); if (search.val() === " ") search.val(""); });
             search.bind("blur", function () { search.removeClass("select2-focused");});
 
             this.dropdown.delegate(resultsSelector, "click", this.bind(function (e) {