--- old/src/java.desktop/unix/classes/sun/awt/X11/XDialogPeer.java	2017-09-08 12:34:05.826823583 -0700
+++ new/src/java.desktop/unix/classes/sun/awt/X11/XDialogPeer.java	2017-09-08 12:34:05.730825522 -0700
@@ -59,6 +59,9 @@
     }
 
     public void setVisible(boolean vis) {
+        if (isDisposed()) {
+            return;
+        }
         XToolkit.awtLock();
         try {
             Dialog target = (Dialog)this.target;