fix: process of records without a ppn (#908) #114

Job	Run time
deny (bans licenses sources)	34s
test (ubuntu-latest, stable, x86_64-unknown-linux-gnu)	1m 11s
deny (advisories)	32s
fuzz (pica-record-ref, fuzz, fuzz-record-ref, 120)	3m 46s
test (ubuntu-latest, beta, x86_64-unknown-linux-gnu)	1m 10s
fuzz (pica-record-matcher, fuzz, fuzz-record-matcher, 200)	4m 48s
test (ubuntu-latest, nightly, x86_64-unknown-linux-gnu)	59s
fuzz (pica-path, fuzz, fuzz-path, 200)	5m 1s
test (windows-latest, stable, i686-pc-windows-msvc)	3m 25s
fuzz (pica-format, fuzz, fuzz-format, 200)	4m 59s
test (macos-latest, stable, x86_64-apple-darwin)	1m 6s
fuzz (pica-query, fuzz, fuzz-query, 200)	4m 59s
msrv	19s
clippy	23s
rustdoc	21s
rustfmt	17s
outdated	4m 47s
udeps	1m 1s
publish	32s
ci	1s
	40m 11s

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