tracks/pony/exercises/beer-song/example.pony in trackler-2.2.1.6 vs tracks/pony/exercises/beer-song/example.pony in trackler-2.2.1.7

@@ -36,9 +36,9 @@
     try
       String.join(
         Iter[USize](Reverse(start, stop))
           .map[String]({(n: USize): String => BeerSong.verse(n) + "\n"})
           .collect(Array[String](start - stop)))
-        .>pop()
+        .>pop()?
     else
       recover String end
     end