Index: trunk/src/org/openstreetmap/josm/gui/preferences/MapPaintPreference.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/preferences/MapPaintPreference.java	(revision 4615)
+++ trunk/src/org/openstreetmap/josm/gui/preferences/MapPaintPreference.java	(revision 4616)
@@ -255,5 +255,10 @@
         @Override
         public Collection<String> serialize(SourceEntry entry) {
-            return Arrays.asList(new String[] {entry.url, entry.name, entry.title, Boolean.toString(entry.active)});
+            return Arrays.asList(new String[] {
+                    entry.url,
+                    entry.name == null ? "" : entry.name,
+                    entry.title == null ? "" : entry.title,
+                    Boolean.toString(entry.active)
+            });
         }
 
Index: trunk/src/org/openstreetmap/josm/gui/preferences/TaggingPresetPreference.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/preferences/TaggingPresetPreference.java	(revision 4615)
+++ trunk/src/org/openstreetmap/josm/gui/preferences/TaggingPresetPreference.java	(revision 4616)
@@ -336,5 +336,5 @@
         @Override
         public Collection<String> serialize(SourceEntry entry) {
-            return Arrays.asList(new String[] {entry.url, entry.title});
+            return Arrays.asList(new String[] {entry.url, entry.title == null ? "" : entry.title});
         }