[Reg : 5.10.1-> 5.11.1] QTreeWidgetItem Partially Checked is broken

Setting Qt::PartiallyChecked to QTreeWidgetItem is broken in 5.11.0 and 5.11.1. 

Steps to reproduce the issue:

1. Execute the attached program with QT 5.10.1, all checkboxes are in the desired state. 
2. Execute the same program with Qt 5.11.0 and 5.11.1, the third checkbox which should be in partial state, is in checked state. 

Expected result: Partial checked checkbox should have correct state. 

Working fine with Windows. Attaching the output snapshots also.