Weird replace error (SOLVED)

[ShotokanTuning]

I have a Access database with field type=Memo.

When I show this field in the browser I use this:

<%
descr = rsVisitReport("Address")
descr = replace(descr, vbCrlf, "<BR>")
Response.Write descr
%>
This works fine with fields that contain data but it returns an error when the Address field is empty.

Microsoft VBScript runtime error '800a005e'

Invalid use of Null: 'replace'

/system/Page.asp, line (number)



So I tried this little code:
<%
if (not rsVisitReport("Address")="") then
descr = rsVisitReport("Address")
descr = replace(descr, vbCrlf, "<BR>")
Response.Write descr
end if
%>
This fixes the old problem and empty fileds are shown correctly but when the field isn't empty and the replace takes place, now give the error:

Microsoft VBScript runtime error '800a005e'

Invalid use of Null: 'replace'

/system/Page.asp, line (number)



I don't get it.