Index: applications/editors/josm/plugins/reltoolbox/src/relcontext/actions/ReconstructPolygonAction.java
===================================================================
--- applications/editors/josm/plugins/reltoolbox/src/relcontext/actions/ReconstructPolygonAction.java	(revision 36132)
+++ applications/editors/josm/plugins/reltoolbox/src/relcontext/actions/ReconstructPolygonAction.java	(revision 36134)
@@ -174,5 +174,8 @@
                                 candidateWay = tmp;
                             }
-                            commands.add(DeleteCommand.delete(Collections.singleton(w)));
+                            final Command deleteCommand = DeleteCommand.delete(Collections.singleton(w));
+                            if (deleteCommand != null) {
+                                commands.add(deleteCommand);
+                            }
                         }
                     }
Index: applications/editors/josm/plugins/reltoolbox/src/relcontext/actions/TheRing.java
===================================================================
--- applications/editors/josm/plugins/reltoolbox/src/relcontext/actions/TheRing.java	(revision 36132)
+++ applications/editors/josm/plugins/reltoolbox/src/relcontext/actions/TheRing.java	(revision 36134)
@@ -399,5 +399,8 @@
         }
         if (!foundOwnWay) {
-            commands.add(DeleteCommand.delete(Collections.singleton(source)));
+            final Command deleteCommand = DeleteCommand.delete(Collections.singleton(source));
+            if (deleteCommand != null) {
+                commands.add(deleteCommand);
+            }
         }
         commands.addAll(relationCommands);