Nullable collectionForAliasSync not marked as such

[moll]

Same problem with GI.Secret's collectionForAliasSync (http://hackage.haskell.org/package/gi-secret-0.0.11/docs/GI-Secret-Objects-Collection.html#v:collectionForAliasSync) as with https://github.com/haskell-gi/haskell-gi/issues/249 — it could return null, but the bindings don't expect so.

It actually throws when I was playing with it:

defaultCollection :: MonadIO io => io Secret.Collection
defaultCollection = Secret.collectionForAliasSync
  Secret.noService "default" [] Gio.noCancellable

(app:13291): libsecret-CRITICAL **: 22:05:30.975: secret_service_read_alias_dbus_path_sync: assertion 'SECRET_IS_SERVICE (self)' failed
app: Received unexpected nullPtr in "collectionForAliasSync".
This is a bug in the introspection data, please report it at
https://github.com/haskell-gi/haskell-gi/issues
CallStack (from HasCallStack):
  checkUnexpectedReturnNULL, called at ./GI/Secret/Objects/Collection.hs:2056:9 in gi-secret-0.0.10-8XK7OMCulsfCa9zBYSvPiX:GI.Secret.Objects.Collection