Fix bug of mal-structured dup group - When a user changes tween type of a tween, the structure of dup group may not satisfy the requirement of new type. - It causes unexpected behavior. - It is fixed by checking structure and remove mal-structured ones.

# -*- indent-tabs-mode: t; tab-width: 8; c-basic-offset: 4; -*-
# vim: sw=4:ts=8:sts=4
m4datadir = $(datadir)/mb
dist_m4data_DATA = foreach.m4 mb_c_header.m4 mb_c_source.m4
dist_bin_SCRIPTS = svg2code.py