bfcorr gives "Index exceeds the number of array elements." error

[pwrightkcl]

Running a pipeline with two images, including segmentation and bias field correction, the bias field correction step crashes with "Index exceeds the number of array elements.". It is looking for a bias-corrected image for each of the segmentation inputs, but there is only one in line 7:
Nii{1}(n) = nifti(pth_seg{7}{n});

Inputs to bf_correct.m:
Nii - 1x1 cell array
Nii{1} - 1x2 nifti
pth_seg - 1x8 cell array
pth_seg{5:7} - 1x1 cell arrays
pth_seg{[1:4,8]} - empty (0x0 double)
pth_seg{7} - 1x1 cell array, with a bias corrected image filename corresponding to the first input image

It looks like the internal SPM function only writes bias corrected for one image. It seems like a decision is needed about whether to limit the user to one bias-corrected image (which may break later steps), or save the bias field and apply it to each image after SPM has finished.