Linux: fixed NPE when using java.awt.TrayIcon (issue #405)

(cherry picked from commit 16a769ea61)

CHANGELOG.md

@@ -14,6 +14,7 @@ FlatLaf Change Log
   `JTable.surrendersFocusOnKeystroke` is `true`) and
   `TextComponent.selectAllOnFocusPolicy` is `once` (the default) or `always`.
   (issue #395)
+- Linux: Fixed NPE when using `java.awt.TrayIcon`. (issue #405)
 
 
 ## 1.6.1

flatlaf-core/src/main/java/com/formdev/flatlaf/FlatLaf.java

@@ -264,6 +264,12 @@ public abstract class FlatLaf
 				}
 			};
 			Toolkit toolkit = Toolkit.getDefaultToolkit();
+
+			// make sure that AWT desktop properties are initialized (on Linux)
+			// before invoking toolkit.addPropertyChangeListener()
+			// https://github.com/JFormDesigner/FlatLaf/issues/405#issuecomment-960242342
+			toolkit.getDesktopProperty( "dummy" );
+
 			toolkit.addPropertyChangeListener( desktopPropertyName, desktopPropertyListener );
 			if( desktopPropertyName2 != null )
 				toolkit.addPropertyChangeListener( desktopPropertyName2, desktopPropertyListener );