cut ops can start on automation tracks too

gtk2_ardour/editor_mouse.cc

@@ -858,6 +858,7 @@ Editor::button_press_handler_1 (ArdourCanvas::Item* item, GdkEvent* event, ItemT
 		case RegionViewNameHighlight:
 		case RegionViewName:
 		case StreamItem:
+		case AutomationTrackItem:
 			_drags->set (new RegionCutDrag (this, item, canvas_event_sample (event)), event, current_canvas_cursor);
 			return true;
 			break;