modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java

@@ -447,12 +447,14 @@
              if (isFocusable() && !hasFocus()) {
                  requestFocus();
                  // The extra simulated mouse pressed event is removed by making the JavaFX scene focused.
                  // It is safe, because in JavaFX only the method "setFocused(true)" is called,
                  // which doesn't have any side-effects when called multiple times.
-                 int focusCause = AbstractEvents.FOCUSEVENT_ACTIVATED;
-                 stagePeer.setFocused(true, focusCause);
+                 if(stagePeer != null) {
+                     int focusCause = AbstractEvents.FOCUSEVENT_ACTIVATED;
+                     stagePeer.setFocused(true, focusCause);
+                 }
              }
          }
  
          sendMouseEventToFX(e);
          super.processMouseEvent(e);