Improve bad access error for std::expected<T, rfl::Error> (#558) #400

Job	Run time
windows-msvc-shared (JSON)	11m 21s
windows-msvc-shared (FLEXBUFFERS)	5m 42s
windows-msvc-shared (CBOR)	9m 25s
windows-msvc-shared (AVRO)	8m 18s
windows-msvc-shared (CAPNPROTO)	7m 45s
windows-msvc-shared (PARQUET)	38m 52s
windows-msvc-shared (MSGPACK)	4m 16s
windows-msvc-shared (YAML)	4m 36s
windows-msvc-shared (TOML)	4m 4s
windows-msvc-shared (UBJSON)	7m 31s
windows-msvc-shared (XML)	4m 9s
windows-msvc (FLEXBUFFERS)	6m 22s
windows-msvc (TOML)	3m 43s
windows-msvc (UBJSON)	7m 8s
windows-msvc (AVRO)	7m 17s
windows-msvc (PARQUET)	39m 31s
windows-msvc (JSON)	10m 33s
windows-msvc (MSGPACK)	3m 34s
windows-msvc (CBOR)	9m 8s
windows-msvc (benchmarks)	48m 16s
windows-msvc (YAML)	4m 26s
windows-msvc (XML)	4m 12s
windows-msvc (CAPNPROTO)	8m 16s
	4h 18m 25s

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