Fix a bug in factions_ui when name is nil

mods/factions/factions.lua

@@ -40,6 +40,11 @@ factions.maximum_faction_inactivity = 604800 -- 1 week
 --! @brief returns whether a faction can be created or not (allows for implementation of blacklists and the like)
 --! @param name String containing the faction's name
 factions.can_create_faction = function(name)
+   -- Can't create faction with nil name
+   if name == nil or name == '' then
+      return false
+   end
+   
     if #name > factions.faction_name_max_length then
         return false
     elseif factions.factions[name] then