[REG 4.8->5.X] Adding QLabel to QHBoxLayout with certain AlignmentFlag(s) (left/right) causes missing repaint

Adding QLabel to QHBoxLayout with certain AlignmentFlags(at least AlignLeft, AlignRight and AlignHCenter) and calling QLabel::setText("") doesn't cause repainting and the old text stays on the label.

Steps:
-Build and run the example app
-Press "Set some text" button => "Some text" will appears on both labels
-Press "Set empty text" button

Actual result:
-Only the above label is empty

Expected result:
-Both labels are empty

Note:
-Both labels are empty after resizing the window