Navigator, Assets, Components and Properties not usable in a new file

Tested with the latest snapshot (from 1.8)

Steps to reproduce:

• Create a new general empty project with default options
• When project is opened, create a new file from File -> New File
• Choose for example Qt Quick Controls -> Custom Button
• After file is created, at least Components, Assets, Properties and Navigator views seem to be "locked" and unusable.
• Switching between Edit mode and Design mode seems to fix the issue