Potential double free in v1.20.0

In file included from /usr/include/glib-2.0/glib.h:116,
                 from ../libmm-glib/mm-common-helpers.h:25,
                 from ../libmm-glib/libmm-glib.h:61,
                 from mm-iface-modem-3gpp-profile-manager.c:22:
In function ‘g_autoptr_cleanup_generic_gfree’,
    inlined from ‘profile_manager_fail_if_connected_bearer’ at mm-iface-modem-3gpp-profile-manager.c:88:31:
/usr/include/glib-2.0/glib/glib-autocleanups.h:30:3: error: ‘apn_type_str’ may be used uninitialized [-Werror=maybe-uninitialized]
   30 |   g_free (*pp);
      |   ^~~~~~~~~~~~
mm-iface-modem-3gpp-profile-manager.c: In function ‘profile_manager_fail_if_connected_bearer’:
mm-iface-modem-3gpp-profile-manager.c:88:31: note: ‘apn_type_str’ was declared here
   88 |             g_autofree gchar *apn_type_str;
      |                               ^~~~~~~~~~~~
cc1: all warnings being treated as errors

https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/blob/1.20.0/src/mm-iface-modem-3gpp-profile-manager.c#L88-90:

            g_autofree gchar *apn_type_str;
            apn_type_str = mm_bearer_apn_type_build_string_from_mask (apn_type);

I think the problem comes from g_autofree.

Context: https://github.com/flathub/org.gnome.Calls/pull/51