The contents of 'test.fits' are irrelevant for this bug; so you can use any FITS image. If you don't have any, you can generate an all-zero FITS image (that is 100x100 pixels) using this command:

$ astarithmetic 100 100 2 makenew -otest.fits

If we use a kernel file for --kernel option in the aststatistic program, there is no problem but if we don't want to use a kernel, we can not use --kernel=none similar to the NoiseChisel program and using this option, aststatistics doesn't run. Also, we don't see a proper error text for it.

To clarify, please see two examples below:

aststatistics test.fits --sky --kernel=kernel.fits
Statistics (GNU Astronomy Utilities) 0.19.16-f4bb
Estimating Sky (reference value) and its STD.
-----------
  - Using 12 CPU threads.
  - Input: test.fits (hdu: 1)
  - Kernel: kernel.fits (hdu: 1)
  - Input convolved with kernel.                       0.254564 seconds
  - Sky and its STD found on 800/4761 tiles.           0.058472 seconds
  - All blank tiles filled (interplated).              0.011181 seconds
  - Smoothed Sky and Sky STD values on tiles.          0.001490 seconds
  - Sky and its STD written to 'test_sky.fits'.
-----------
Completed in: 0.563517 seconds
-----------

aststatistics test.fits --sky --kernel=none

FITSIO status = 104: could not open the named file
failed to find or open the following file: (ffopen)
none[1#]
aststatistics: opening the given extension/HDU in the given file