print_matrix is broken for SubArrays

[stevengj]

Running a = [1,2,3,4]; b = sub(a, 1:2) in the repl gives

2-element SubArray of 4-element Int64 Array:
 #undef
 #undef

The culprit seems to be somewhere in print_matrix (since print_matrix(STDOUT, b) gives the two #undefs).

[johnmyleswhite]

I'd bet that the problem is that SubArray doesn't implement a matrix style getindex for vectors. Does a quick hack like getindex(s::SubArray, i::Integer, j::Integer) = getindex(s, i) restore printing something that's not #undef?