Fix too large output view when central toolbar is deactivated

git-svn-id: http://svn.code.sf.net/p/texstudio/code@4141 92cce386-e96d-4106-809f-596c673a3fd8
don't allow to collapse EditorTabs or OutputView in their splitter

git-svn-id: http://svn.code.sf.net/p/texstudio/code@4142 92cce386-e96d-4106-809f-596c673a3fd8