Qt delivers warning about setGeometry on opening a dialog

Getting following warning on opening a dialog:

QWindowsWindow::setGeometry: Unable to set geometry 400x30+484+358 on QWidgetWindow/'ZProgressDialog_cClassWindow'. Resulting geometry: 400x91+484+358 (frame: 8, 31, 8, 8, custom margin: 0, 0, 0, 0, minimum size: 400x91, maximum size: 16777215x16777215)

Steps to reproduce:

Run attcahed project

Expected Result: No warning should be there

Actual result : Getting following warning : 

setGeometry: Unable to set geometry 241x111+1600+790 on QWidgetWindow/'WidgetClassWindow'. Resulting geometry: 292x111+1600+790 (frame: 16, 72, 16, 16, custom margin: 0, 0, 0, 0, minimum size: 241x111, maximum size: 16777215x16777215).

This was not the case with Qt 5.6.1.

As Workaround, setMinimumSize(20,20) in its constructor, helps to get rid of this warning.

As per my understanding, its size is determined by the layout and its children widgets. So setting the minimal size should normally not be necessary. 

So, creating a defect to get developer's team view.