Allow empty titles

scripts/memes.coffee

@@ -23,6 +23,7 @@ module.exports = (robot) ->
            sapere sapere come funziona il comando'
 
   escape = (str) ->
+    return '_' unless str.length
     str.replace( /-/g, '--')
        .replace(/\ /g,  '-')
        .replace( /_/g, '__')
@@ -42,10 +43,8 @@ module.exports = (robot) ->
       names = template.aliases
       res.send (gen_meme names[0], title, names.join ', '),
                if robot.adapterName is 'tg' then cb else ''
-
       cb() if robot.adapterName isnt 'tg'
 
-
   robot.respond /meme (.+)/i, (res) ->
     args = (i.trim() for i in res.match[1].split ',')
     return res.send usage if args.length != 3