Index: trunk/src/org/openstreetmap/josm/gui/progress/PleaseWaitProgressMonitor.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/progress/PleaseWaitProgressMonitor.java	(revision 4755)
+++ trunk/src/org/openstreetmap/josm/gui/progress/PleaseWaitProgressMonitor.java	(revision 4756)
@@ -287,7 +287,9 @@
             @Override
             public void run() {
-                dialog.setInBackgroundPossible(PleaseWaitProgressMonitor.this.taskId != null && Main.isDisplayingMapView());
-                reset();
-                getDialog();
+                if (dialog != null) {
+                    dialog.setInBackgroundPossible(PleaseWaitProgressMonitor.this.taskId != null && Main.isDisplayingMapView());
+                    reset();
+                    getDialog();
+                }
             }
         });