Please describe the problem:
The buttons in the "Save to Disk" dialog becomes unresponsive.

Steps to reproduce:
1. Save a calendar or todo list to the disk
2. Enter a name without an extension in the file chooser dialog
3. Press Save and answer No to the "Do you want to continue" dialog


Actual results:
The buttons in the file chooser dialog becoms unresponsive and you have to close
the dialog.

Expected results:
The buttons should still work.

Does this happen every time?
Yes

Other information:
The "The file has no extension. Do you want to contiune?" dialog is quite
unnecessary. The file could just be saved with the extension appended to the
given filename.