Fixed memory leak. Each of the toolbar modes (view, foci, borders, volume)...

Fixed memory leak.  Each of the toolbar modes (view, foci, borders, volume) may provide a widget that is added to the toolbar.  The widget only had a parent when it was displayed in the toolbar.  Those toolbar mode widgets not displayed in the toolbar were never deleted resulting in leaked memory and a potential to cause a crash.  The code has been updated to fix this problem.