Differentiate between a minCharacters of 0 and undefined.

The comment at line 65 implies that setting minCharacters to 0 will result in no matches being displayed when there are no characters in the search box (e.g. if you've backspaced your search term). The code was treating 'undefined' and 0 identically.

Author: neomindryan

jquery.ui.autocomplete.js

@@ -136,7 +136,7 @@
        * @return container (which should be positioned and visible)
        */
       updateList: function(unfilteredList, val) {
-        if (opt.minCharacters && val.length <= opt.minCharacters) {
+        if (typeof opt.minCharacters !== 'undefined' && val.length <= opt.minCharacters) {
           return false;
         }