Index: trunk/src/org/openstreetmap/josm/actions/JosmAction.java
===================================================================
--- trunk/src/org/openstreetmap/josm/actions/JosmAction.java	(revision 5025)
+++ trunk/src/org/openstreetmap/josm/actions/JosmAction.java	(revision 5026)
@@ -123,5 +123,7 @@
 
     public void setTooltip(String tooltip) {
-        putValue(SHORT_DESCRIPTION, Main.platform.makeTooltip(tooltip, sc));
+        if (tooltip != null) {
+            putValue(SHORT_DESCRIPTION, Main.platform.makeTooltip(tooltip, sc));
+        }
     }