app: run errors_init() after gimp_load_config().

Since error handling is based on preferences, the config needs to be
loaded first. Otherwise the gimp->config object does not exist yet and
we get a bunch of "'G_IS_OBJECT (object)' failed" assertion which
recurse in error handling when trying to get the "debug-policy"
property.
Just init the error handling later. It means it won't handle early
loading code, but that is not much of an issue.

app/app.c

@@ -276,18 +276,21 @@ app_run (const gchar         *full_prog_name,
 
   g_object_unref (gimpdir);
 
+  gimp_load_config (gimp, alternate_system_gimprc, alternate_gimprc);
+
   /* Initialize the error handling after creating/migrating the config
    * directory because it will create some folders for backup and crash
    * logs in advance. Therefore running this before
    * gimp_user_install_new() would break migration as well as initial
    * folder creations.
+   *
+   * It also needs to be run after gimp_load_config() because error
+   * handling is based on Preferences. It means that early loading code
+   * is not handled by our debug code, but that's not a big deal.
    */
   errors_init (gimp, full_prog_name, use_debug_handler,
                stack_trace_mode, backtrace_file);
 
-
-  gimp_load_config (gimp, alternate_system_gimprc, alternate_gimprc);
-
   /*  run the late-stage sanity check.  it's important that this check is run
    *  after the call to language_init() (see comment in sanity_check_late().)
    */