Shell-quoting garbled after parsing UTF-8 characters

```sh
#! /bin/ksh
LANG=C.UTF-8
printf '%q\n' 'Is shell-quoting garbled?'
print -nr $'\303\274' | read -n1 g
printf '%q\n' 'Is shell-quoting garbled?'
```

When running this, the second line is output without the final quote.

When you run this with `set -x`, the issue happens to quoted strings in the xtrace as well, suggesting that the global shell-quoting algorithm is somehow affected.