[Lazarus] Fpsreadsheet bug?

[Werner Pamler]

Thanks for sharing the file and for your pre-analysis which helped me to 
find the bug quickly. It is fixed in fpspreadsheet r6047. If you want to 
stick to your currently installed version 1.8.4 you must patch the 
function TsSpreadBiffReader.Fixfont in unit xlscommon by adding these 
lines immediately after the "begin":

function TsSpreadBIFFReader.FixFontIndex(AFontIndex: Integer): Integer;
var
   fnt: TsFont;
begin
   // --- begin insert ---
   if FFontList.Count = 0 then
   begin
     Result := 0;
     exit;
   end;
   // --- end insert ---

   fnt := TsFont(FFontList[AFontIndex]);
   [...]