application: Show the window right
If we have at least one active call, show the call window, else show the main window.
This isn't necessarily a complete patch, but should be good enough. As it was said that there will be two separate windows (!18 (comment 7531)), we have to make exceptions when showing windows.
The following cases are fixed in this patch:
- If the user closed the main window, create one if required and show that
- if the call window has at least one active call, show the calls window.