Index: /trunk/src/org/openstreetmap/josm/gui/bbox/SourceButton.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/bbox/SourceButton.java	(revision 19310)
+++ /trunk/src/org/openstreetmap/josm/gui/bbox/SourceButton.java	(revision 19311)
@@ -82,5 +82,6 @@
 
             // attempt to initialize button group matching current state of slippyMapBBoxChooser
-            buttonModel.setSelected(this.slippyMapBBoxChooser.getTileController().getTileSource().getId().equals(ts.getId()));
+            String tsid = this.slippyMapBBoxChooser.getTileController().getTileSource().getId();
+            buttonModel.setSelected(tsid != null && tsid.equals(ts.getId()));
         }