fpspreadsheet: grid fix if FWorksheet not assigned from Aleksey Lagunov, issue #26521, thank you.

git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@3371 8e941d3f-bd1b-0410-a28a-d453659cc2b4

components/fpspreadsheet/fpspreadsheet.pas

@@ -1,7 +1,7 @@
 {
 fpspreadsheet.pas
 
-Writes an spreadsheet document
+Writes a spreadsheet document
 
 AUTHORS: Felipe Monteiro de Carvalho
 }

components/fpspreadsheet/fpspreadsheetgrid.pas

@@ -1175,6 +1175,7 @@ end;
 }
 procedure TsCustomWorksheetGrid.DrawFrozenPaneBorders(ARect: TRect);
 begin
+  if FWorkSheet = nil then exit;
   if (soHasFrozenPanes in FWorksheet.Options) then begin
     Canvas.Pen.Style := psSolid;
     Canvas.Pen.Color := clBlack;