Guard BookmarksRunner thread use
Summary:
Krunner::match is performed in potentially multiple overlapping threads
as a user presses each character. Qt SQL is not thread safe according to
the docs or according to the numerous reports.
It's a bit of a blind patch, ideally we should only use the database in
the thread that opened it.
This patch at least this means queries will be queued which I think will
be enough.
CCBUG: 363136
Test Plan: Restarted krunner. Still saw my firefox bookmarks
Reviewers: Plasma, mart
Reviewed By: Plasma, mart
Subscribers: rempt, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D12683