Don't try to filter null key combinations
When using composite key combinations, kwin would do random weird
actions when the first key was pressed (e.g. ` key). This makes sure we
are not trying to match.
Reviewers: KWin, graesslin
Reviewed By: KWin, graesslin
Subscribers: graesslin, kwin, KWin
Differential Revision: https://phabricator.kde.org/D12416