Guard CharacterOrder_Save against empty char list

CHARACTER_LIST_UPDATE can fire with numChars == 0 in a transient state
when returning to the glue screen after /logout, before the server's
SMSG_CHAR_ENUM re-populates the character list. Without this guard,
CharacterOrder_Save writes an empty string to the vault, wiping the
saved order. The real CHARACTER_LIST_UPDATE that follows then reads
that empty string in Apply, returns early, and leaves the table at
server-default identity order — sort order silently reset.

Fix: skip the write when numChars is 0. The only legitimate zero case
is a brand-new account with no characters, where there's nothing to
persist anyway.

CharacterSelect.lua

@@ -685,6 +685,12 @@ function CharacterOrder_Save()
 	local realm = GetServerName() or "";
 	if ( realm == "" ) then return; end
 	local numChars = GetNumCharacters();
+	-- Skip when the list is empty. CHARACTER_LIST_UPDATE can fire in a
+	-- transient state (returning to glue after logout, before the server's
+	-- SMSG_CHAR_ENUM populates the list) where numChars is briefly 0.
+	-- Writing an empty string here would wipe the saved order before the
+	-- real update arrives to Apply it.
+	if ( numChars == 0 ) then return; end
 	local names = {};
 	for i = 1, numChars do
 		local name = GetCharacterInfo(GetCharIDFromIndex(i));