Minor fix for JS error when using undefined extra_data_text element

main/admin/user_list.php

@@ -94,14 +94,14 @@ function display_advanced_search_form () {
 $(document).ready(function() {
 
     var select_val = $("#input_select_extra_data").val();
-
-    if (select_val != 0) {
-        document.getElementById(\'extra_data_text\').style.display="block";
-        document.getElementById(\'input_extra_text\').value = "";
-    } else {
-        document.getElementById(\'extra_data_text\').style.display="none";
+    if ( document.getElementById(\'extra_data_text\')) {
+        if (select_val != 0) {
+            document.getElementById(\'extra_data_text\').style.display="block";
+            document.getElementById(\'input_extra_text\').value = "";
+        } else {
+            document.getElementById(\'extra_data_text\').style.display="none";
+        }
     }
-
 });
 
 </script>';