Fixes undo/redo with tangents editing

	The tangents editing logic was missing adding a journalling
checkpoint, hence the undo/redo wasn't working properly.
	This commit fixes it.

src/gui/editors/AutomationEditor.cpp

@@ -627,6 +627,8 @@ void AutomationEditor::mousePressEvent( QMouseEvent* mouseEvent )
 			{
 				if (m_pattern->progressionType() == AutomationPattern::CubicHermiteProgression)
 				{
+					m_pattern->addJournalCheckPoint();
+
 					// Gets the closest node to the mouse click
 					timeMap::iterator node = getClosestNode(mouseEvent->x());