How to convert Map to array?

[Sean Eskapp]

I'm trying to use the array() function in std.array to convert a transformed
array using map (std.algorithm) back to a dynamic array, from a Map. I keep
getting a cryptic error "object.Exception at C:\Program Files
(x86)\D\dmd2\windows\bin\..\..\src\phobos\std\
algorithm.d(426): Cannot reduce an empty range w/o an explicit seed value.".
Am I misunderstanding how this is supposed to work?