"Use AJAX to reload other fields of type Select..." Issue

I have this control app that has 2 select fields, one for state and other for City. State field is configured such that if changed, City reloads by ajax. See attached screenshot.

This works but each time I change State (i.e. it fetches the correct set of cities in the state,) but it also shows a blank prompt box (titled “Output”) with no message and I have to click Close to get rid of it. This is a simple thing I’ve done in so many apps without problems and don’t know why it’s happening here. I’ve rechecked the automatic SQL query on which the selects are populated: no probs there.

Last resort would be to redo the app from scratch but this would be time consuming hence my posting here for any help.

ajax select issue.jpg

Application > Error settings > Ajax Error Output > No.