Fix infinite loop caused by invalid UTF-8 bytes #2324

Job	Run time
cargo bench	1m 10s
cargo clippy	34s
cargo +stable build	1m 4s
codegen	30s
cargo +beta build	1m 24s
cargo +1.36 build (futures-{core, io, sink})	3m 42s
cargo +nightly build	1m 23s
cargo doc	31s
cargo hack check --feature-powerset	29s
cargo fmt	6s
cargo minimal-versions build	48s
cargo miri test	10m 53s
cargo build --target thumbv7m-none-eabi	27s
cargo build --target thumbv6m-none-eabi	25s
cargo test -Z sanitizer=address	4m 11s
cargo test (ubuntu-latest)	4m 20s
cargo test -Z sanitizer=memory	4m 13s
cargo +1.56 build	2m 43s
cargo test (macos-latest)	5m 46s
cargo test -Z sanitizer=thread	3m 28s
cargo test (windows-latest)	6m 22s
cargo test (ubuntu-latest, aarch64-unknown-linux-gnu)	4m 51s
cargo test (ubuntu-latest, armv7-unknown-linux-gnueabihf)	8m 6s
cargo test (ubuntu-latest, armv5te-unknown-linux-gnueabi)	9m 7s
cargo test (ubuntu-latest, i686-unknown-linux-gnu)	5m 39s
	1h 22m 12s

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