when u login with no name or username, it causes a null

any1 no how ot make it not make a null?

my gues is something like

if (playernameLength <= 0) {
s.close();
}

idk.. DOES ANY1 NO???

i need 2 no this 4 2 reasons

1) it makes a null
2) i only alow 1 acc per ip cuz of a dupe, was only fix i culd think of