If during runtime buffer per window gets turned off an exception might occur:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
        at javax.swing.BufferStrategyPaintManager$BufferInfo.windowClosed(BufferStrategyPaintManager.java:888)
        at java.awt.AWTEventMulticaster.windowClosed(AWTEventMulticaster.java:302)
        at java.awt.Window.processWindowEvent(Window.java:1593)
        at javax.swing.JDialog.processWindowEvent(JDialog.java:591)
        at java.awt.Window.processEvent(Window.java:1548)
        at java.awt.Component.dispatchEventImpl(Component.java:4365)
        at java.awt.Container.dispatchEventImpl(Container.java:2018)
        at java.awt.Window.dispatchEventImpl(Window.java:2202)
        at java.awt.Component.dispatchEvent(Component.java:4195)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)
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