Fix build --withincluded-modules
Fix build --withincluded-modules

According to Doug Felt:

pango's configure dies with --with-included-modules=yes, because when
have_libthai is true, thai_modules ends up being ",thai-lang", and
all_modules (and included_modules) ends up containing ',,'.

for module in $included_modules;

ends up with module='' and the case $module falls back to default, which
calls as_fn_error.

Distrotech/pango,danny-ku/pango,Distrotech/pango,Distrotech/pango,danny-ku/pango,danny-ku/pango