Runtime error '91' when trying to exit Do...Loop

[Cloudfall]

I get the "Runtime error '91' " message when trying to exit a
Do...Loop. My code is as follows:

Dim cell As Range
Dim sFirst As String
:
Else
Set cell = Nothing
End If
Loop Until cell Is Nothing Or sFirst = cell.Address

I have stepped through this code. Everything works fine until I get to:

'Else', then 'Set cell = Nothing', 'End If' (the "Locals Window" tells
me that 'cell' contains 'Nothing', 'sFirst' contains "$D$4"), 'Loop
Until cell Is Nothing Or sFirst = cell.Address', and then when I try to
step to the next line it generates:

"Runtime error '91': Object variable or With block variable not set."

The code works if I comment out "Or sFirst = cell.Address" as in the
following line:

Loop Until cell Is Nothing 'Or sFirst = cell.Address

It's hard to imagine that there is something wrong with 'sFirst =
cell.Address' as the following line of code worked earlier in this
program without any problem:

"If Not cell Is Nothing And cell.Address <> sFirst Then"

I really have no idea what is going on here. Does anybody out there
know? Thank you.

 

[JE McGimpsey]

If cell is Nothing, then cell doesn't have an .Address property. Since
both arguments of And are evaluated, you'll always get an error.

Do you need to set cell to Nothing?

 

[Cloudfall]

Thank you for your Fast(!) reply. I probably don't need to set cell to
Nothing. Now that this mystery has been solved, I can more confidently
make changes to the code. If you're an Australian, I hope you win a big
trifecta on the Melbourne Cup tomorrow!!! All the best.