Bug: Stack Vector Sum example broken

[dpharris]

Your change to loops broke the example.

This works:
[1,2,3] 0 1 rotate { drop + } loop
or:
[1,2,3]0,1r{d+}l

A larger list is nicer: [1,2,3,4,5,6,7,8]0,1r{d+}l

[mikaelpatel]

Yes, forgot that. Thanks for the reminder.

[mikaelpatel]

Please see commit 85df422.