"Inster keyframe" in item properties is not selectable after creating a timeline.

Steps to reproduce:

1. Create a project
2. Drag a rectangle from item library to the Form Editor
3. Create a timeline
4. In properties view, click the icon beside Position X property to open the menu
5. -> Insert keyframe is not selectable (see picture) and clicking it wont insert the keyframe
6. Click something else in the navigator, e.g. the root Rectangle and then choose the added rectangle again
7. -> Insert keyframe is now selectable and clicking it will insert the keyframe