Fix for Menu problem in #226

Qt’s menu imll appears to be buggy, it will disappear, and then show up
forever after switching back to the app. This deletes the menu when
it’s not in use in order to solve the problem.
Qt 5+ - Make Last column resizable (Qt looks terrible doing this)

The last column was fixed, probably because Qt does not react well to
having the last column resizable. Oh well.