re-introduced invalid case to vtk enum

MeshLib/VtkOGSEnum.cpp

@@ -92,6 +92,8 @@ int OGSToVtkCellType(CellType ogs)
 			return VTK_PYRAMID;
 		case CellType::PYRAMID13:
 			return VTK_QUADRATIC_PYRAMID;
+		case CellType::INVALID:
+			return -1;
 		default:
 			return -1;
 	}