Please describe the problem:
If the @ref in =cell("contents", @ref) contains a sheet reference, the function
returns the contents of the corresponding cell on the current sheet, instead of
the sheet named in @ref.

Steps to reproduce:
1. Create new Gnumeric file w/at least two sheets.
2. Put 'foo' into Sheet1!A1
3. Put 'bar' into Sheet2!A1
4. Put '=cell("contents",Sheet1!A1)' into Sheet2!A2


Actual results:
The displayed result is "bar".

Expected results:
The expected result is "foo".

Does this happen every time?
Yes.

Other information:
* Verified that Excel has the expected behavior.
* The obvious workaround (=Sheet1!A1) doesn't work if the cell is blank (the
cell function returns blank, but the direct reference returns 0).