applets/taskmanager: fix tooltip text with custom window title

The logic here makes an assumption that the window title will always be in the form of "[window title] — [app name] [optional KWin numerical suffix]" which is not always the case, and breaks when this assumption is not met. Exceptions to that pattern used to be rare, but now we are doing it in several of our own apps, and it's also possible for users to set custom titles in Chromium, so it's not so rare anymore.

To handle this case, add an early return that handles the custom window title.

There is no regression for the common case.

BUG: 462760 FIXED-IN: 5.27.5

Before	After

cc @fusionfuture