Ensure average players stat is never more than max player count.

mods/lobby/stats.lua

@@ -40,8 +40,11 @@ function lobby.retrieve_stats(map_id)
       local traitor = stats.winner_traitor
       local team = stats.winner_team
       local avg_players = stats.player_count
-      local avg = string.format("%.2f", avg_players)
       local max = stats.max_players or 0
+      if avg_players > max then
+         avg_players = max
+      end
+      local avg = string.format("%.2f", avg_players)
       formspec =
          'formspec_version[3]'..
          'size[16,9]'..