Part: modernize C++11

* use nullptr

src/Mod/Part/App/PointPyImp.cpp

@@ -111,7 +111,7 @@ PyObject* PointPy::toShape(PyObject *args)
     try {
         if (!this_point.IsNull()) {
             if (!PyArg_ParseTuple(args, ""))
-                return 0;
+                return nullptr;
 
             BRepBuilderAPI_MakeVertex mkBuilder(this_point->Pnt());
             const TopoDS_Vertex& sh = mkBuilder.Vertex();
@@ -121,11 +121,11 @@ PyObject* PointPy::toShape(PyObject *args)
     catch (Standard_Failure& e) {
 
         PyErr_SetString(PartExceptionOCCError, e.GetMessageString());
-        return 0;
+        return nullptr;
     }
 
     PyErr_SetString(PartExceptionOCCError, "Geometry is not a point");
-    return 0;
+    return nullptr;
 }
 
 Py::Float PointPy::getX(void) const
@@ -191,7 +191,7 @@ void PointPy::setZ(Py::Float Z)
 
 PyObject *PointPy::getCustomAttributes(const char* /*attr*/) const
 {
-    return 0;
+    return nullptr;
 }
 
 int PointPy::setCustomAttributes(const char* /*attr*/, PyObject* /*obj*/)