Fix kpropertiesdialog "Points to" path resolving incorrectly from desktop
Currently "Points to" button resolves paths from the desktop that start with "desktop:" incorrectly, this fixes that issue and also fixes relative path traversal for the button.
This change seems to fix the issue for the different use cases I threw at it, but it is possible I'm missing something.
For more info about the bug, read the bug report below.