When the desktop file has Terminal=true (e.g. htop), it should be launched in a terminal.
Instead of calling "kstart5 -- ", this calls "kstart5 --application " when and only when:
- kstart5 is available
- the desktop file is in XDG_DATA_HOME/applications/, not XDG_DATA_HOME/kglobalaccel/
- we are launching the desktop file's main group, not other actions