Basic error check in `saveNIfTIs.m`

Make sure the NIfTI is at least a size that we can save.

IO/saveNIfTIs.m

 function saveNIfTIs(D, directory, params)
 
+assert(mod(params.V, 100) == 0, '`params.V` must be divisible by 100!')
+
 % Prepare NIfTI
 vsize = [1 1 1 params.TR];
 vtype = 'f';