Math Domain Error

[DominikRh]

Dear authors,
I am using pybdsf to remove sources from artificial maps. Out of the 200 maps from this one particular run, one specific map results in a math domain error with the following console output:

Traceback (most recent call last):
  File "python-pybdsf-scripts/pybdsf-8.py", line 18, in <module>
    img = bdsf.process_image(input_image, quiet=True, frequency=850e9, beam = (14./3600, 14./3600, 0.), ncores=8)
  File "/users/drhiem/.local/lib/python2.7/site-packages/bdsf/__init__.py", line 253, in process_image
    img.process(**kwargs)
  File "/users/drhiem/.local/lib/python2.7/site-packages/bdsf/image.py", line 135, in process
    success = interface.process(self, **kwargs)
  File "/users/drhiem/.local/lib/python2.7/site-packages/bdsf/interface.py", line 62, in process
    _run_op_list(img, op_chain)
  File "/users/drhiem/.local/lib/python2.7/site-packages/bdsf/__init__.py", line 152, in _run_op_list
    op(img)
  File "/users/drhiem/.local/lib/python2.7/site-packages/bdsf/gaul2srl.py", line 61, in __call__
    src_index, source = self.process_CM(img, g_list, isl, src_index)
  File "/users/drhiem/.local/lib/python2.7/site-packages/bdsf/gaul2srl.py", line 194, in process_CM
    isl, delc, subn, subm)
  File "/users/drhiem/.local/lib/python2.7/site-packages/bdsf/gaul2srl.py", line 319, in process_Multiple
    mompara = func.momanalmask_gaus(subim_src, mask, isrc, bmar_p, True)
  File "/users/drhiem/.local/lib/python2.7/site-packages/bdsf/functions.py", line 583, in momanalmask_gaus
    mompara[4] = sqrt((m2[0]+m2[1]-sqrt((m2[0]-m2[1])*(m2[0]-m2[1])+4.0*m11*m11))/(2.0*tot))*fwsig
ValueError: math domain error

As far as I can tell, there is nothing unusual about this map, and as mentioned, this is the only map out of 200 with the same statistical properties where this error occurs. I have uploaded both the map and the log file here:
https://drive.google.com/drive/folders/12jSFdvqpWKZVZI8jTvyuxHEpYnL_rWLx?usp=sharing