line 13 is the code for the trigger for the search behavior:
if ((isset($_GET["Search_x"]) && $_GET["Search_x"] != "")) {
note the _x at the name of the variable:
Search_x
this is for an image element which has no value, but passes the x and y coordinates.
remove the _x portion so it can work with the standard submit button:
if ((isset($_GET["Search"]) && $_GET["Search"] != "")) {