Error in incoming message dialog: next

[sander]

When I click on the next button, I get this error:

can't read "next": no such variable
can't read "next": no such variable
    while executing
"return $next"
    (procedure "::MailBox::GetNextMsgID" line 14)
    invoked from within
"::MailBox::GetNextMsgID $msgIdDisplay"
    (procedure "::GotMsg::NextMsg" line 6)
    invoked from within
"::GotMsg::NextMsg"
    invoked from within
".jgotmsg.frall.f.b.btnext invoke "
    invoked from within
".jgotmsg.frall.f.b.btnext instate {pressed !disabled} { .jgotmsg.frall.f.b.btnext state !pressed; .jgotmsg.frall.f.b.btnext invoke } "
    (command bound to event)

[Mats (matsben)]

My suspicion is that this bug is a side effect of a previous bug with this dialog. I have nevertheless taken some action to prevent it.