QuickDesigner: Preview does update Slider not on first open

Steps to reproduce:

• create Quick Controls app from template
• switch with the qml doc opened to the Designer
• drag a Slider onto the preview
• change some of the values (give it a nice maximum and a value between min and max)
• switch back to Editor
• switch back to Designer
• Slider's value in the preview seems to be 0
• go to the Slider's Value property and change this (e.g. I did just mark a digit before the '.' and typed another digit)
• now the Slider gets updated to reflect the changed value

Note: this works for e.g. ProgressBar, Calendar, CheckBox