FIX: Remove doubled-up fix for divide-by-zero warning

Author: effigies

nibabel/processing.py

@@ -302,8 +302,6 @@ def smooth_image(img,
     # Voxel sizes
     RZS = img.affine[:, :n_dim]
     vox = np.sqrt(np.sum(RZS ** 2, 0))
-    # Avoid divisions by zero for 4+D images
-    vox[3:] = 1
     # Smoothing in terms of voxels
     vox_fwhm = fwhm / vox
     vox_sd = fwhm2sigma(vox_fwhm)