You have used a field for which there is no “”previous”” value as the argument for the Previous or PreviousIsNull function, or you have used a field for which there is no “”next”” value as the argument for the Next or NextIsNull function.
Una kutumika uwanja ambayo hakuna “”awali”” thamani kama hoja kwa kazi Previous au PreviousIsNull, au una kutumika uwanja kwa ambayo hakuna “”pili”” thamani kama hoja kwa ijayo au NextIsNull kazi.