protected long optionalFooterLength() throws CartInvalidCartException {
		return optionalFooterLength;
	}
Get the length of the optional footer. Should be 0 if no optional footer is
available.

@return The length of the optional footer, 0 if no optional footer.
@throws CartInvalidCartException If the footer object is not valid.
Ghidra/Features/FileFormats/src/main/java/ghidra/file/formats/cart/CartV1Footer.java