Qt Creator crashes when switching to design mode

I am experiencing crashes of the QT Creator after clicking on the design mode button. 

The QmlDesigner plugin is installed and loaded.

The following steps lead to a crash of the QT Creator:

1. Create a new Project ( Application (Qt for Python) -> Qt Quick Application - Empty)
2. Double-click the main.qml file.
3. Click on Design

After Step 3 the Qt Creator crashes and closes. (No error message appears on the screen).

It is still possible to open the design mode for the project:

Start QT Creator

1. File -> Open File With -> open a .qml File
2. (Open the file with Qt Quick Designer when asked )
3. Click on Design
4.  Design window is opened now.
5. Open the new Project again
6. Click on Design
7. The Design mode can be used now for the project.

Thank you!