Update gui.lua

lol new to github, left some comments in the script, but i'll add my 2 cents here too. 

edit location: TextChanged Function

fix 1
this is a bug I found while entering my nickname, [ABK]Necro.
if characters [ ( or % are typed as the first character in the filter you get an error for every character typed after it.
the error occurred in the string.find, I just kinda worked around it and made it so if the first character was [ ( or % then always show all names in list

not really a major issues since its a client side error, but an its error.

fix 2
tried to filter for just Necro... nothing.
the way it was the player's name needed to match filter text from the first character up
made it so if it found the filter's text anywhere in a player's name, make it visable.

no errors fixed here just makes it more functionable