private void applyColorsThatConcealTheEmptyRows() {
/* display the NA() values in light gray so they are less visible */
SheetConditionalFormatting cf = s.getSheetConditionalFormatting();
ConditionalFormattingRule rule = cf.createConditionalFormattingRule("ISNA(A1)");
FontFormatting fontFmt = rule.createFontFormatting();
fontFmt.setFontColorIndex(IndexedColors.GREY_25_PERCENT.index);
String range;
if (maxCol() != null) {
range = String.format("A1:%s1048576", maxCol().toString(Utils.getCaf()));
} else {
// TODO fix in a different way