quadcc - can someone trigger this error message for me?

looking at tweaking a quadcc error message slightly to make a patch for
integral easier.  currently, there's an error message in three places near
lines 1829, 1962, 2053 (i shifted them already by a couple lines, but
that's close):

if (fvals.length () != 1 || ! fvals(0).is_real_matrix ())
 error ("quadcc: integrand F must return a single, real-valued vector")
...

i want to split that into two checks with separate error messages, and add
a test for each, but I can't find a test input to trigger the
"fvals.length() != 1" part.  The few things I've tried always trigger the
following instead:

if (effex.numel () != ex.numel ())
              error ("quadcc: integrand F must return a single, real-valued
vector of the same size as the input");

can someone who understands the quadcc code better than me mess around with
simple, test inputs to produce the first error but not because of
the real/complex check?