Fail to add_FSF to a source at the egde of the field
When creating a source at the edge of the field with a size that make it go over the extent of the FITS file, adding the FSF to the source fails. In this illustration:
the source white map is correctly extended over the cube spatial coverage (the green box overlap the red limit) but when add_FSF is executed, the field map is cut within the limits of the FITS file and multiplying the weight map by the source white map in source.py:1235 fails because the white map is larger in one of the spatial axis.