Part: [skip ci] allow to create empty shapes of each type

src/Mod/Part/App/TopoShapeCompoundPyImp.cpp

@@ -59,6 +59,13 @@ PyObject *TopoShapeCompoundPy::PyMake(struct _typeobject *, PyObject *, PyObject
 // constructor method
 int TopoShapeCompoundPy::PyInit(PyObject* args, PyObject* /*kwd*/)
 {
+    if (PyArg_ParseTuple(args, "")) {
+        // Undefined Compound
+        getTopoShapePtr()->setShape(TopoDS_Compound());
+        return 0;
+    }
+
+    PyErr_Clear();
     PyObject *pcObj;
     if (!PyArg_ParseTuple(args, "O", &pcObj))
         return -1;
@@ -79,7 +86,6 @@ int TopoShapeCompoundPy::PyInit(PyObject* args, PyObject* /*kwd*/)
         }
     }
     catch (Standard_Failure& e) {
-
         PyErr_SetString(PartExceptionOCCError, e.GetMessageString());
         return -1;
     }