After batch-processing the userinfo, the authority state advanced the
parse pointer onto the '@' and relied on the end-of-loop increment to
step past it. That increment uses the byte length of the authority's
first code point, not the delimiter's. When the first code point was
multi-byte, the pointer overshot into the middle of a code point and
the next iteration sliced the string at a non-char boundary causing the
process to panic. We now step past the delimiter explicitly so we don't
need to rely on the end of loop increment to do so.
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