Atmospheric correction fails if no DEM is available.

2018/01/31 13:59:48 [27212816]:
An error occurred during atmospheric correction. BE AWARE THAT THE SCENE 27212816 (ENTITY ID S2A_OPER_MSI_L1C_TL_SGS__20160723T144844_A005668_T31UFA_N02.04) HAS NOT BEEN ATMOSPHERICALLY CORRECTED! Error message was:
TypeError("ufunc 'isnan' not supported for the input types, and the inputs could not be safely coerced to any supported types according to the casting rule ''safe''",)

2018/01/31 13:59:48 [27212816]:   Traceback (most recent call last):
  File "/home/gfz-fe/scheffler/python_deployed/gms_preprocessing/gms_preprocessing/algorithms/L1C_P.py", line 819, in run_atmospheric_correction
    self.results = ac_gms(rs_image, self.options, logger=self.logger, script=script)
  File "/home/gfz-fe/scheffler/python_deployed/sicor/sicor/sicor_ac.py", line 731, in ac_gms
    s2img.dem_missing_fraction = (np.sum(np.isnan(s2img.dem)) + np.sum(s2img.dem == 0.0)) / np.prod(s2img.dem.shape)
TypeError: ufunc 'isnan' not supported for the input types, and the inputs could not be safely coerced to any supported types according to the casting rule ''safe''