Fix rubber band not going away after right-click

Summary: Fix rubber band not going away after right-click in the folder view

Test Plan:
Hold left click
Drag to make rubber band
Right click

Reviewers: #dolphin, ngraham, elvisangelaccio

Reviewed By: #dolphin, ngraham

Subscribers: elvisangelaccio, ngraham, kfm-devel

Tags: #dolphin

Differential Revision: https://phabricator.kde.org/D21590