Exit if there is no value for hint.

Author: Tomas Kirda

src/jquery.autocomplete.js

@@ -507,6 +507,10 @@
                 value = that.el.val().toLowerCase(),
                 bestMatch = null;
 
+            if (!value) {
+                return;
+            }
+
             $.each(that.suggestions, function (i, suggestion) {
                 var foundMatch = suggestion.value.toLowerCase().indexOf(value) === 0;
                 if (foundMatch) {