+ handle case when workbench fails to be created, fix problem when inserting menu

src/Gui/Application.cpp

@@ -1006,6 +1006,8 @@ bool Application::activateWorkbench(const char* name)
             type = result.as_std_string("ascii");
             if (Base::Type::fromName(type.c_str()).isDerivedFrom(Gui::PythonBaseWorkbench::getClassTypeId())) {
                 Workbench* wb = WorkbenchManager::instance()->createWorkbench(name, type);
+                if (!wb)
+                    throw Py::RuntimeError("Failed to instantiate workbench of type " + type);
                 handler.setAttr(std::string("__Workbench__"), Py::Object(wb->getPyObject(), true));
             }
 

src/Gui/Workbench.cpp

@@ -789,7 +789,7 @@ ToolBarItem* TestWorkbench::setupCommandBars() const
 
 // -----------------------------------------------------------------------
 
-TYPESYSTEM_SOURCE(Gui::PythonBaseWorkbench, Gui::Workbench)
+TYPESYSTEM_SOURCE_ABSTRACT(Gui::PythonBaseWorkbench, Gui::Workbench)
 
 PythonBaseWorkbench::PythonBaseWorkbench()
   : _menuBar(0), _contextMenu(0), _toolBar(0), _commandBar(0), _workbenchPy(0)
@@ -858,10 +858,13 @@ void PythonBaseWorkbench::appendMenu(const std::list<std::string>& menu, const s
     MenuItem* item = _menuBar->findItem( *jt );
     if (!item)
     {
-        Gui::MenuItem* wnd = _menuBar->findItem( "&Windows" );
         item = new MenuItem;
         item->setCommand( *jt );
-        _menuBar->insertItem( wnd, item );
+        Gui::MenuItem* wnd = _menuBar->findItem( "&Windows" );
+        if (wnd)
+            _menuBar->insertItem(wnd, item);
+        else
+            _menuBar->appendItem(item);
     }
 
     // create sub menus