QmlDesigner: clear texteditor view statusbar

- when puppet is restarted
 - when the view is attached (switching document, switching mode)

Change-Id: I06a4acf78a18b893bca9f7cd3d2bae74dc3459aa
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

src/plugins/qmldesigner/components/texteditor/texteditorview.cpp

@@ -93,6 +93,7 @@ TextEditorView::~TextEditorView()
 void TextEditorView::modelAttached(Model *model)
 {
     Q_ASSERT(model);
+    m_widget->clearStatusBar();
 
     AbstractView::modelAttached(model);