Fix memory leak in KUrlNavigatorPlacesSelector::updateMenu
This method gets called each time solid notices a change, which can in some
setups be very frequent. It leaked memory as the submenus and their actions
were not deallocated properly.
Test Plan: Builds. User feedback: "so far so good, 160 MB Memory usage". It was ~7GiB before this patch.
Reviewers: Frameworks, davidedmundson, meven
Reviewed By: davidedmundson, meven
Subscribers: anthonyfieroni, meven, kde-frameworks-devel
Differential Revision: https://phabricator.kde.org/D27002