feat(prosody): Updates checks in presence_identity avoids setting missing user.

resources/prosody-plugins/mod_presence_identity.lua

 -- values are set in the session, then insert them into the presence messages
 -- for that session.
 function on_message(event)
-    if event and event["stanza"] then
-      if event.origin and event.origin.jitsi_meet_context_user then
-
+    local stanza, session = event.stanza, event.origin;
+    if stanza and session then
           update_presence_identity(
-              event.stanza,
-              event.origin.jitsi_meet_context_user,
-              event.origin.jitsi_meet_context_group
+              stanza,
+              session.jitsi_meet_context_user,
+              session.jitsi_meet_context_group
           );
-
-      end
     end
 end
 

resources/prosody-plugins/util.lib.lua

 -- @param creator_group the group of the user who created the user which
 -- presence we are updating (this is the poltergeist case, where a user creates
 -- a poltergeist), optional.
-function update_presence_identity(
-    stanza, user, group, creator_user, creator_group)
+function update_presence_identity(stanza, user, group, creator_user, creator_group)
 
     -- First remove any 'identity' element if it already
     -- exists, so it cannot be spoofed by a client
             end
             return tag
         end
-    )
+    );
+
+    if not user then
+        return;
+    end
 
     stanza:tag("identity"):tag("user");
     for k, v in pairs(user) do