Suggested optimization for Utf8.length()

Wanted to suggest a small optimization. It is quite common for applications to do a quick check (along with null-ness) for 0-length of string-typed fields. Today's Utf8.length() implementation is:

return toString().length;

I believe this could easily get optimized to return this instead:

return length == 0 ? 0 : toString().length();

Thus avoiding the need to create the string representation for this common use case (and scenario).