Index: trunk/src/org/openstreetmap/josm/gui/dialogs/FilterDialog.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/dialogs/FilterDialog.java	(revision 14894)
+++ trunk/src/org/openstreetmap/josm/gui/dialogs/FilterDialog.java	(revision 14895)
@@ -259,4 +259,6 @@
             public String getToolTipText(MouseEvent e) {
                 int index = columnModel.getColumnIndexAtX(e.getPoint().x);
+                if (index == -1)
+                    return null;
                 int realIndex = columnModel.getColumn(index).getModelIndex();
                 return COLUMN_TOOLTIPS[realIndex];