plasmashell: Check for null view in ShellCorona::panelContainmentDestroyed
when applying a new layout, panelContainmentDestroyed will be called when m_panelViews is already empty, so we need to check on auto view = m_panelViews.take(cont);
(cherry picked from commit 5141a83c)
6d0d96e6 Check for null view in ShellCorona::panelContainmentDestroyed
Co-authored-by: Marco Martin notmart@gmail.com