modules/graphics/src/main/java/com/sun/glass/ui/Window.java

@@ -1,7 +1,7 @@
 /*
- * Copyright (c) 2010, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2010, 2018, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Oracle designates this

@@ -293,10 +293,13 @@
 
         this.ptr = _createChildWindow(parent);
         if (this.ptr == 0L) {
             throw new RuntimeException("could not create platform window");
         }
+        if (screen == null) {
+            screen = Screen.getMainScreen(); // start with a default
+        }
     }
 
     public boolean isClosed() {
         Application.checkEventThread();
         return this.ptr == 0L;