fix: resolve multiplayer compile and style CI failures

Agent-Logs-Url: https://github.com/winnerspiros/osu/sessions/d825f8ce-9334-4f69-94c3-e55a5c9b1871

Co-authored-by: winnerspiros <1675249+winnerspiros@users.noreply.github.com>

Author: Copilot

osu.Game/Screens/OnlinePlay/Multiplayer/Participants/ParticipantPanel.cs

@@ -304,7 +304,7 @@ private void updateState()
 
                 // If the mods are updated at the end of the frame, the flow container will skip a reflow cycle: https://github.com/ppy/osu-framework/issues/4187
                 // This looks particularly jarring here, so re-schedule the update to that start of our frame as a fix.
-                Schedule(() => userModsDisplay.Current.Value = userRuleset == null ? [] : user.Mods.Select(m => m.ToMod(userRuleset)).ToList());
+                Schedule(() => userModsDisplay.Current.Value = userRuleset == null ? [] : slot.User.Mods.Select(m => m.ToMod(userRuleset)).ToList());
             }
 
             userStateDisplay.UpdateStatus(current.Value);

osu.Game/Tests/Visual/Multiplayer/TestMultiplayerClient.cs

@@ -643,8 +643,7 @@ private async Task changeMatchType(MatchType type)
 
                     foreach (var user in ServerRoom.Users)
                     {
-                        if (headToHeadRoomState.Slots != null)
-                            headToHeadRoomState.Slots[i++] = user.UserID;
+                        headToHeadRoomState.Slots?[i++] = user.UserID;
 
                         user.MatchState = null;
                         await ((IMultiplayerClient)this).MatchUserStateChanged(clone(user.UserID), clone(user.MatchState)).ConfigureAwait(false);
@@ -659,8 +658,7 @@ private async Task changeMatchType(MatchType type)
 
                     foreach (var user in ServerRoom.Users)
                     {
-                        if (teamVersusRoomState.Slots != null)
-                            teamVersusRoomState.Slots[i++] = user.UserID;
+                        teamVersusRoomState.Slots?[i++] = user.UserID;
 
                         user.MatchState = new TeamVersusUserState();
                         await ((IMultiplayerClient)this).MatchUserStateChanged(clone(user.UserID), clone(user.MatchState)).ConfigureAwait(false);