Nulldate Filter Outsystems/SQL

((@dt_inicio = @Nulldate and @dt_fim = @Nulldate) OR
((CAST(FLOOR(CAST( {EMAIL}.[Created_DateTime] as FLOAT)) AS DATETIME)) >= @dt_inicio AND
(CAST(FLOOR(CAST( {EMAIL}.[Created_DateTime] as FLOAT)) AS DATETIME)) <= @dt_fim)) AND
({EMAIL}.[Subject] LIKE ('%' + @SearchKeyword + '%') OR {EMAIL}.[Message] LIKE ('%' + @SearchKeyword + '%') OR @SearchKeyword = NULL)