Index: trunk/src/org/openstreetmap/josm/gui/conflict/pair/relation/RelationMemberTableCellEditor.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/conflict/pair/relation/RelationMemberTableCellEditor.java	(revision 4477)
+++ trunk/src/org/openstreetmap/josm/gui/conflict/pair/relation/RelationMemberTableCellEditor.java	(revision 4478)
@@ -34,4 +34,8 @@
 
     public Component getTableCellEditorComponent(JTable table, Object value, boolean isSelected, int row, int column) {
+        // Do not edit empty or incomplete members ! (fix #5374 and #6315)
+        if (value == null)
+            return null;
+
         RelationMember member = (RelationMember)value;