When using sessions->save session nothing happens unless sessions->save session as or sessions->open session or the like was invoked first. This is misleading as one might suppose that a 'default' session is saved in the background. It would be much better if the sessions->save session as dialog would be shown in such a case (this would also improve consistency as the same behavior is used for saving unnamed files; invoking file->save on any unnamed file actually causes the dialog triggered by file->save as to show).

reproduce:
- start kate w/out any session
- open a few documents
- select session->save session

expected behavior:
- the dialog "specify new name for current session" is shown
- the session is saved using the given name

actual behavior:
- afaik nothing happens and the save silently fails

Reproducible: Always