We should never serialize any shorthand when one of the longhands is missing.
<rdar://problem/103423965>
Pull request: https://github.com/WebKit/WebKit/pull/7770
Committed 258038@main (a7f14bf80bc9): <https://commits.webkit.org/258038@main> Reviewed commits have been landed. Closing PR #7770 and removing active labels.