kirigami_package_breeze_icons: don't treat lists as elements

Summary:
GLOB_RECURSE will give us a list, treat it as such.
Also when the list has more than just one item, pick the first as the best
candidate.
Some cases like help-about has more than one and it fails currently.

CCBUG: 396626

Reviewers: mart, vkrause, andreaska

Reviewed By: mart

Subscribers: plasma-devel

Tags: Kirigami

Differential Revision: https://phabricator.kde.org/D14299