WPSUniqueValues plugin hangs on malformed response

[Gnafu]

If autocomplete feature on SpatialSelectorQueryForm receives an unexpected response, the autocomplete suggestions panel hangs on "loading...".

Use case:

• Configure SpatialSelectorQueryForm with autocomplete
• Set the autocomplete url to a valid WPS service that requires authentication
• Try any query

The service requires authentication, but the request is anonymous, so an xml exception is returned and the "loading..." text is still there.