Multi-screen engine doesn't handle correctly some cases.
Example:
1. Run mc.
2. Open some file in internal editor.
3. Switch back to the file panels.
4. Open another file in internal editor. As a result, two editors are opened.
5. Close current editor. Now you are in file panels.
6. Run screen list dialog (Meta-`).
6a. The 1st editor is highlighted as current screen. This is wrong.
Current screen is file panels.
6b. Cannot switch to the opened editor in this dialog.
Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
