[macOS] Checkbox created by calling QTreeWidgetItem::setCheckState() fails to follow macOS style guidelines

A checkbox created by calling QTreeWidgetItem::setCheckState() fails to follow macOS style guidelines: When checked, the checkbox should stay blue while the application is active, but, due to a bug the checkbox turns gray when the treewidget loses focus.

Steps to reproduce:

• Run the sample attached on macOS
• Check both checkboxes
• Click on the line edit to move focus
  EXPECTED: Both checkboxes should stay blue
  ACTUAL: The checkbox inside the treewidget turns gray