[runners/converter] Skip empty parts when splitting units
Summary:
Skip empty parts when splitting the units(D27166: Refactor converter runner).
PS: I had to set the locale to german to reproduce this issue,
thats why I didn't noticed it in the first place.
Test Plan: Does not display results for queries like 1/2
Reviewers: broulik
Reviewed By: broulik
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D28458