+ make sure that Sketch.clear() doesn't allow any arguments

src/Mod/Sketcher/App/SketchPyImp.cpp

@@ -141,6 +141,9 @@ PyObject* SketchPy::addConstraint(PyObject *args)
 
 PyObject* SketchPy::clear(PyObject *args)
 {
+    if (!PyArg_ParseTuple(args, ""))
+        return 0;
+
     getSketchPtr()->clear();
 
     Py_RETURN_NONE;