restoration of setDrawingInProgress solves the most flagrant crashes in mask editor

now projections are crashing; more repairs to come ...

GUI/View/Mask/MaskGraphicsScene.cpp

@@ -153,7 +153,7 @@ void MaskGraphicsScene::cancelCurrentDrawing()
     if (m_drawing_in_progress) {
         ASSERT(m_currentItem);
         m_maskContainerModel->removeMask(m_currentItem.get());
-        m_drawing_in_progress = false;
+        setDrawingInProgress(false);
     }
 }
 
@@ -303,7 +303,7 @@ void MaskGraphicsScene::mouseReleaseEvent(QGraphicsSceneMouseEvent* event)
                 // making item beneath of mouse release position to be selected
                 makeViewAtMousePosSelected(event);
             }
-            m_drawing_in_progress = false;
+            setDrawingInProgress(false);
         }
     } else
         QGraphicsScene::mouseReleaseEvent(event);