Load Project Window cannot be closed when evoked through the context menu in Projects sidebar

The 'Load Project' window, which appears when clicking the 'Load project' entry in the context menu (right-click) in the 'Projects' tab from the standard sidebar, cannot be closed.

A ButtonPushed action is animated on the 'Cancel' button in that window, the same as when hitting the 'esc' key, but the window is not closing, also the red cross from the window decoration is inactive. Moreover, the whole application cannot be closed at all ( usually done by the CMD+Q combination ). The only way to terminate is to kill the process manually.

For the project loading itself, the window shows the same buggy behavior as described in QTCREATORBUG-11234.