Index: /trunk/src/org/openstreetmap/josm/gui/layer/markerlayer/PlayHeadMarker.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/layer/markerlayer/PlayHeadMarker.java	(revision 12578)
+++ /trunk/src/org/openstreetmap/josm/gui/layer/markerlayer/PlayHeadMarker.java	(revision 12579)
@@ -123,5 +123,7 @@
         Main.map.selectMapMode(oldMode);
         Main.map.mapView.repaint();
-        timer.start();
+        if (timer != null) {
+            timer.start();
+        }
     }