+ fix crash due to sloppy reference counting

src/Gui/ApplicationPy.cpp

@@ -891,6 +891,8 @@ PyObject* Application::sDoCommand(PyObject * /*self*/, PyObject *args,PyObject *
     if (!PyArg_ParseTuple(args, "s", &pstr))     // convert args: Python->C 
         return NULL;                             // NULL triggers exception
     Command::doCommand(Command::Doc,pstr);
+
+    Py_INCREF(Py_None);
     return Py_None;
 }
 
@@ -900,6 +902,8 @@ PyObject* Application::sDoCommandGui(PyObject * /*self*/, PyObject *args,PyObjec
     if (!PyArg_ParseTuple(args, "s", &pstr))     // convert args: Python->C
         return NULL;                             // NULL triggers exception
     Command::runCommand(Command::Gui,pstr);
+
+    Py_INCREF(Py_None);
     return Py_None;
 }
 
@@ -909,6 +913,8 @@ PyObject* Application::sAddModule(PyObject * /*self*/, PyObject *args,PyObject *
     if (!PyArg_ParseTuple(args, "s", &pstr))     // convert args: Python->C
         return NULL;                             // NULL triggers exception
     Command::addModule(Command::Doc,pstr);
+
+    Py_INCREF(Py_None);
     return Py_None;
 }
 
@@ -917,5 +923,7 @@ PyObject* Application::sShowDownloads(PyObject * /*self*/, PyObject *args,PyObje
     if (!PyArg_ParseTuple(args, ""))             // convert args: Python->C 
         return NULL;                             // NULL triggers exception 
     Gui::Dialog::DownloadManager::getInstance();
+
+    Py_INCREF(Py_None);
     return Py_None;
 }

src/Mod/Path/App/CommandPyImp.cpp

@@ -167,6 +167,7 @@ PyObject* CommandPy::setFromGCode(PyObject *args)
     if (PyArg_ParseTuple(args, "s", &pstr)) {
         std::string gcode(pstr);
         getCommandPtr()->setFromGCode(gcode);
+        Py_INCREF(Py_None);
         return Py_None;
     }
     throw Py::Exception("Argument must be a string");
@@ -211,6 +212,7 @@ PyObject *CommandPy::getCustomAttributes(const char* attr) const
             if (getCommandPtr()->Parameters.count(satt)) {
                 return PyFloat_FromDouble(getCommandPtr()->Parameters[satt]);
             }
+            Py_INCREF(Py_None);
             return Py_None;
         }
     }

src/Mod/Path/App/PathPyImp.cpp

@@ -189,6 +189,7 @@ PyObject* PathPy::setFromGCode(PyObject * args)
     if (PyArg_ParseTuple(args, "s", &pstr)) {
         std::string gcode(pstr);
         getToolpathPtr()->setFromGCode(gcode);
+        Py_INCREF(Py_None);
         return Py_None;
     }
     throw Py::Exception("Argument must be a string");

src/Mod/Path/App/TooltablePyImp.cpp

@@ -436,6 +436,7 @@ PyObject* TooltablePy::addTools(PyObject * args)
         Path::Tool &tool = *static_cast<Path::ToolPy*>(o)->getToolPtr();
         getTooltablePtr()->addTool(tool);
         //return new TooltablePy(new Path::Tooltable(*getTooltablePtr()));
+        Py_INCREF(Py_None);
         return Py_None;
     }
     PyErr_Clear();
@@ -448,6 +449,7 @@ PyObject* TooltablePy::addTools(PyObject * args)
             }
         }
         //return new TooltablePy(new Path::Tooltable(*getTooltablePtr()));
+        Py_INCREF(Py_None);
         return Py_None;
     }
     Py_Error(Base::BaseExceptionFreeCADError, "Wrong parameters - tool or list of tools expected");
@@ -461,6 +463,7 @@ PyObject* TooltablePy::setTool(PyObject * args)
         Path::Tool &tool = *static_cast<Path::ToolPy*>(o)->getToolPtr();
         getTooltablePtr()->setTool(tool,pos);
         //return new TooltablePy(new Path::Tooltable(*getTooltablePtr()));
+        Py_INCREF(Py_None);
         return Py_None;
     }
     Py_Error(Base::BaseExceptionFreeCADError, "Wrong parameters - expected tool and optional integer");
@@ -474,8 +477,12 @@ PyObject* TooltablePy::getTool(PyObject * args)
         {
             Path::Tool tool = getTooltablePtr()->getTool(pos);
             return new ToolPy(new Path::Tool(tool));
-        } else
+        }
+        else
+        {
+            Py_INCREF(Py_None);
             return Py_None;
+        }
     }
     Py_Error(Base::BaseExceptionFreeCADError, "Argument must be integer");
 }
@@ -486,6 +493,7 @@ PyObject* TooltablePy::deleteTool(PyObject * args)
     if (PyArg_ParseTuple(args, "|i", &pos)) {
         getTooltablePtr()->deleteTool(pos);
         //return new TooltablePy(new Path::Tooltable(*getTooltablePtr()));
+        Py_INCREF(Py_None);
         return Py_None;
     }
     Py_Error(Base::BaseExceptionFreeCADError, "Wrong parameters - expected an integer (optional)");