#1301 Cancel save file dialog under Session->File->New file still clears input area

[sfst]

Using Session -> File -> New file asks whether we want to save now if we have unsaved input. If we click "Yes", but then use "Cancel" in the dialog to save the file the input area still will be cleared.

Undo (Ctrl-Z) does work, but that might not be obvious to all users.

Also if we just click the "X" to close any of the 2 dialogs the input area still is cleared.