Under X Window, mouse input is locked when stopping on a breakpoint inside JavaFX event handler

While debugging a sample Ensemble application (from http://www.oracle.com/technetwork/java/javafx/samples/) the mouse is locked after hitting a breakpoint at ensemble.controls.SearchBox:245 (though keyboard remains operational).

To reproduce: start the app, type something in a search box at the top, and choose any result.

Looks like JavaFX variant of http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6714678.