This is because you have wrong autocomplete source, which is supposed to be an array, or a string or a function. In your case, the response function lacks
return
statement which is a main part defining the autocomplete data.
Please see:
http://api.jqueryui.com/autocomplete/#option-source[
^].
Pay attention for the sample "Using a custom source callback to match only the beginning of terms".
See also:
http://api.jqueryui.com/autocomplete/[
^].
—SA