modules/graphics/src/main/java/com/sun/javafx/tk/quantum/WindowStage.java

@@ -806,11 +806,11 @@
         /*
          * RT-17588 - exit if stage is closed from under us as 
          *            any further access to the Glass layer 
          *            will throw an exception
          */
-        if (enabled && platformWindow.isClosed()) {
+        if (enabled && platformWindow == null || platformWindow.isClosed()) {
             return;
         }
         setPlatformEnabled(enabled);
         if (enabled) {
             if (isAppletStage && null != appletWindow) {

@@ -819,13 +819,15 @@
         }
     }
 
     // Note: This method is required to workaround a glass issue mentioned in RT-12607
     protected void requestToFront() {
+        if (platformWindow != null) {
         platformWindow.toFront();
         platformWindow.requestFocus();
     }
+    }
 
     public void setInEventHandler(boolean inEventHandler) {
         this.inEventHandler = inEventHandler;
     }