Fix bug 374921: Tool view grouping no longer works in 5.1 branch

Summary:
This commit fixes view grouping, broken in D3170 revision.

BUG: 373213

Test Plan: Tested on 5.1 and master branches.

Reviewers: apol, KDevelop, mwolff

Reviewed By: KDevelop, mwolff

Subscribers: mwolff, kdevelop-devel

Differential Revision: https://phabricator.kde.org/D4219