Fix player addition logic in match handling

Prevent adding a player to matchPlayers if userIndex is not found.

src/routes/tournaments/[tournamentguid]/matches/[matchGuid]/+page.svelte

@@ -821,7 +821,7 @@
                 ...matchPlayers.slice(userIndex + 1)
             ];
         } else {
-            matchPlayers = [...matchPlayers, params[0]];
+            return;
         }
     }