g_string_insert_c: assertion 'pos <= string->len' failed

Hi hackers,

I am trying make check and installcheck from the head of master
(to test my application/script branch), on Red Hat EL 7.4,
and I am seeing instances of:

GLib-CRITICAL **: g_string_insert_c: assertion 'pos <= string->len' failed

For example, the common-src/hexencode test fails on that assertion.

Am I the only person to see this?

-Chap