add connection_get_jid()

Use a singleton `Jid` inside the connection instead of always re-creating
a `Jid` from the same string.

Signed-off-by: Steffen Jaeckel <jaeckel-floss@eyet-services.de>

src/xmpp/muc.c

@@ -882,8 +882,7 @@ muc_members_add(const char* const room, const char* const jid)
         if (g_hash_table_insert(chat_room->members, strdup(jid), NULL)) {
 #ifdef HAVE_OMEMO
             if (chat_room->anonymity_type == MUC_ANONYMITY_TYPE_NONANONYMOUS) {
-                auto_char char* our_barejid = connection_get_barejid();
-                if (strcmp(jid, our_barejid) != 0) {
+                if (strcmp(jid, connection_get_barejid()) != 0) {
                     omemo_start_session(jid);
                 }
             }