Measure: Fix quick measure

* Create QuickMeasure in C++ instead of Python to avoid that it will be garbage collected
* Handle exceptions in case of invalid selections
* Refactor QuickMeasure class
* Fix linter warnings

src/Mod/Measure/Gui/AppMeasureGui.cpp

@@ -20,7 +20,9 @@
  **************************************************************************/
 
 #include "PreCompiled.h"
-
+#ifndef _PreComp_
+#include <QApplication>
+#endif
 #include <Base/Console.h>
 #include <Base/Interpreter.h>
 #include <Base/PyObjectBase.h>
@@ -71,7 +73,7 @@ PyMOD_INIT_FUNC(MeasureGui)
         PyErr_SetString(PyExc_ImportError, "Cannot load Gui module in console application.");
         PyMOD_Return(nullptr);
     }
-    
+
     // load dependent module
     try {
         Base::Interpreter().loadModule("Measure");
@@ -97,7 +99,11 @@ PyMOD_INIT_FUNC(MeasureGui)
 
 //    Q_INIT_RESOURCE(Measure);
 
-    Base::Interpreter().addType(&MeasureGui::QuickMeasurePy::Type, mod, "QuickMeasure");
+    Base::Interpreter().addType(&MeasureGui::QuickMeasurePy::Type, mod, "QuickMeasure");
+
+    // Create a QuickMeasure instance
+    auto measure = new MeasureGui::QuickMeasure(QApplication::instance());
+    Q_UNUSED(measure)
 
     PyMOD_Return(mod);
 }