gtk+3: temporary copy to fix immodules issue

A TypeError exception occurs due to trying to join a None value returned by
do_split_packages. This occurred because it was trying to split immodules when
there were no immodules to split, so only split if there are immodules. When
upstream merges the fix, we can drop this.

Signed-off-by: Christopher Larson <chris_larson@mentor.com>