memory (disco): fix return value for disco_infos bridge method:

empty `language` (`None`) was not converted to empty string, resulting in bridge error.

libervia/backend/memory/disco.py

@@ -443,8 +443,8 @@ class Discovery:
         await defer.DeferredList(defer_list)
         return found_entities
 
-    @defer.inlineCallbacks
-    def _disco_infos(
+    @ensure_deferred
+    async def _disco_infos(
         self, entity_jid_s, node="", use_cache=True, profile_key=C.PROF_KEY_NONE
     ):
         """Discovery method for the bridge
@@ -456,7 +456,7 @@ class Discovery:
         """
         client = self.host.get_client(profile_key)
         entity = jid.JID(entity_jid_s)
-        disco_infos = yield self.get_infos(client, entity, node, use_cache)
+        disco_infos = await self.get_infos(client, entity, node, use_cache)
         extensions = {}
         # FIXME: should extensions be serialised using tools.common.data_format?
         for form_type, form in list(disco_infos.extensions.items()):
@@ -478,7 +478,7 @@ class Discovery:
         return (
             [str(f) for f in disco_infos.features],
             [
-                (cat, type_, lang, identity.name or "")
+                (cat, type_, lang or "", identity.name or "")
                 for (cat, type_), lang_identities in list(disco_infos.identities.items())
                 for lang, identity in lang_identities.items()
             ],