[kcm] Handle empty shortcut in property fetch
Summary:
.first() wasn't guarded with a check of
the list size.
BUG: 416397
FIXED-IN: 5.18.0
Reviewers: Plasma, ngraham
Reviewed By: ngraham
Subscribers: ngraham, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D26772