My GTFS stops.txt has a problem. It says "stops.txt contains an invalid non-numerical value for the stop_lat field"

The provider said the latitude field can be blank. But, it keeps me from generating transit lines and stops in ArcMAP. Could there be any solution for this? Can any transit authorities provide GTFS dataset that does not work in ArcGIS?

I will really appreciate your help.

P.S. the error message is attached to this email.

Thanks,

Hoon