7072645: Toolkit.addPropertyChangeListener(name, pcl) throws NPE for null name

Reviewed-by: art

src/solaris/classes/sun/awt/X11/XToolkit.java

@@ -1532,6 +1532,10 @@ public final class XToolkit extends UNIXToolkit implements Runnable {
     }
 
     public synchronized void addPropertyChangeListener(String name, PropertyChangeListener pcl) {
+        if (name == null) {
+            // See JavaDoc for the Toolkit.addPropertyChangeListener() method
+            return;
+        }
         initXSettingsIfNeeded(name);
         super.addPropertyChangeListener(name, pcl);
     }

src/windows/classes/sun/awt/windows/WToolkit.java

@@ -879,6 +879,10 @@ public class WToolkit extends SunToolkit implements Runnable {
     }
 
     public synchronized void addPropertyChangeListener(String name, PropertyChangeListener pcl) {
+        if (name == null) {
+            // See JavaDoc for the Toolkit.addPropertyChangeListener() method
+            return;
+        }
         if ( WDesktopProperties.isWindowsProperty(name)
              || name.startsWith(awtPrefix)
              || name.startsWith(dndPrefix))