Dear all,

as reported by Richard - although without a testcase - we leak
gmp memory in do_subscript().  The attached patch was derived
by inspection of the code pointed at by valgrind and regtested
on x86_64-pc-linux-gnu.

Committed as obvious as

commit r13-6336-g45f406c4f62e516b58dcda20b5a7aa43ff0aa0f3
Author: Harald Anlauf <anlauf@gmx.de>
Date: Fri Feb 24 19:56:32 2023 +0100

Thanks,
Harald