Signed-off-by: Rémi Denis-Courmont <rdenis@simphalempin.com>

This bug can never happen, as we never call with pppsz_longname == NULL
at the moment.

I believe this path cannot be triggered at the moment however, as
there quite few block_Realloc users. Fixes CID#197.

(it's not distinct from the module bank lock)

Unfortunately(?), these only occur in multi-instances scenarii...