Bug Fixes in KDE Base
Fix handling of unknown mimetypes.
If there are no associated apps, or the mimetype is wrong/unknown, then use
KRun to show an open-with dialog or determine the mimetype correctly.
Same logic as in KonqMainWindow.
My testcase was an attached MESSAGE/RFC822 (uppercase, so unknown) file in Jira.
(cherry picked from commit 528fb4202ff7d55d693b6f175322f2acf0d6e753)