go/scanner: fall back to next() when encountering 0 bytes in parseIdentifier
CL 308611 optimized parseIdentifier for ASCII, but inadvertently skipped
error handling for 0 bytes. Don't take the optimized path when
encountering 0.
Fixes #46855
Change-Id: Ic584e077eb74c012611fefa20eb71ca09c81b3c7
Reviewed-on: https://go-review.googlesource.com/c/go/+/329790
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>