Core auth not validating player names

[S-S-X]

mineunit/auth.lua

Lines 37 to 42 in 15adf6c

	function auth.read(name)
	if not entries[name] then
	entries[name] = AuthEntry(name)
	end
	return entries[name]
	end

This should validate player name and prevent AuthEntry constructor with invalid player names.

Also AuthEntry should not be called with nonexistent player in first place, make sure that player exists before constructing AuthEntry.
Only construct AuthEntry if player exists (included in mineunit:get_players() table).