[Bug fortran/67567] resolve.c: gfc_error called with iface->module == NULL

[zeccav at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67567

--- Comment #2 from Vittorio Zecca <zeccav at gmail dot com> ---
Unfortunately I do not master gdb and gcc internals enough for that.
The check costs two instructions on my x86-64.