AttributeError: 'NoneType' object has no attribute 'is_empty' when trying to set new CRS

I have geodataframe that has two geometry fields.
I’m trying to set new CRS but every time I get the next error message:

AttributeError: ‘NoneType’ object has no attribute ‘is_empty’

when I am able to check the original CRS of the layer:

print('original crs is:',tost.crs)

>>>original crs is: EPSG:4326

but then when I try to set new CRS to the copy:

tast = tost.copy()
tast= tast.to_crs({'init': 'epsg:3857'})
print('projected the copy df to:',tast.crs)

>>>AttributeError: 'NoneType' object has no attribute 'is_empty'

I don’t understand why is this hapenning.
What cause this error?
My goal here is to be able to set the crs

from shapely.geometry.collection import GeometryCollection

tast['geometry'] = tast.geometry.apply(lambda x: x if x else GeometryCollection())

tast.to_crs({'init': 'epsg:3857'})