Update msc wrt Condition blocks

mscgraphics/basicmscgraph/mscGraphBasicMSCScene.py

@@ -132,7 +132,7 @@ class MscGraphBasicMSCScene(QGraphicsScene):
 
     def removeInstance(self, instance):
         u""" Remove a Instance from Scene """
-        self._bmsc.removeInstance(instance)
+        self.bmsc().removeInstance(instance)
         self.removeItem(instance)
         instance.delete()
 
@@ -243,7 +243,8 @@ class MscGraphBasicMSCScene(QGraphicsScene):
 
     def removeCondition(self, condition):
         condition.delete()
-        self.removeItem(condition)
+        if condition.scene():
+            self.removeItem(condition)
     #**************************************************************************
     # Actions
     #**************************************************************************