delete exclusive dependencies when deleting items from project explorer

app/window/mainwindow/mainwindowundo.cpp

@@ -35,4 +35,14 @@ void OpenSequenceCommand::undo()
   Core::instance()->main_window()->CloseSequence(sequence_);
 }
 
+void CloseSequenceCommand::redo()
+{
+  Core::instance()->main_window()->CloseSequence(sequence_);
+}
+
+void CloseSequenceCommand::undo()
+{
+  Core::instance()->main_window()->OpenSequence(sequence_);
+}
+
 }

app/window/mainwindow/mainwindowundo.h

@@ -43,6 +43,24 @@ private:
 
 };
 
+class CloseSequenceCommand : public UndoCommand
+{
+public:
+  CloseSequenceCommand(Sequence* sequence) :
+    sequence_(sequence)
+  {}
+
+  virtual void redo() override;
+
+  virtual void undo() override;
+
+  virtual Project* GetRelevantProject() const override {return nullptr;}
+
+private:
+  Sequence* sequence_;
+
+};
+
 }
 
 #endif // MAINWINDOWUNDO_H