PD: Mirror feature should be more permissive

If you have a mirror feature and set the mirror plane with the normal feature editing the recompute works. But if the mirror plane is set with the property editor then the recompute fails with the message that no mirror plane reference is set.

This is related to a an empty sub-name list of the link property instead of a single and empty sub-name element.

This PR allows to specify a sketch, plane or datum plane without a sub-name.

For more details see: https://forum.freecad.org/viewtopic.php?t=86568

This fixes #13238

src/Mod/PartDesign/App/FeatureTransformed.cpp

@@ -183,9 +183,13 @@ App::DocumentObjectExecReturn *Transformed::execute()
     try {
         std::list<gp_Trsf> t_list = getTransformations(originals);
         transformations.insert(transformations.end(), t_list.begin(), t_list.end());
-    } catch (Base::Exception& e) {
+    }
+    catch (Base::Exception& e) {
         return new App::DocumentObjectExecReturn(e.what());
     }
+    catch (const Standard_Failure& e) {
+        return new App::DocumentObjectExecReturn(e.GetMessageString());
+    }
 
     if (transformations.empty())
         return App::DocumentObject::StdReturn; // No transformations defined, exit silently