Fix "values are not the same" error in replicate_row when repinfo value is a '0'

Fix "values are not the same" error in replicate_row when repinfo value is a '0'

When check_replicate_row tested for valid values before starting the check, if the actual value returned was 0 it would evaluate to false, resulting in the error:
	"Cannot test replication: values are not the same"

This is resolved by simply checking if the value is defined before assigning it's value a blank string instead.