Well, in that case you need to find a way to edit this AVAILABLE_OUTFITS constant in the client. But even then I doubt it would work, the client is probably allocating an array with size 50, that is why the assertion is in place, if it tried to store more than 50 outfits, it would overflow the array.
It seems you just can't send more than 50 outfits, maybe you should change the way the player chooses his outfit, this is what I would do: whenever the player clicks Set Outfit, send a modal window with all the outfits he has, he chooses one and then the outfit window is sent, with just that outfit so the player can choose his colors. It is not optimal but it *might* work.