Media: Prevent Multisite fatal error in legacy file rewrites. #22761

Job	Run time
Determine Matrix	2s
Single Site Default / Test before	14m 6s
Single Site Default / Test current	13m 42s
Multisite Default / Test before	13m 38s
Multisite Default / Test current	13m 48s
Single Site Memcached / Test before	13m 29s
Single Site Memcached / Test current	14m 15s
Multisite Memcached / Test before	14m 7s
Multisite Memcached / Test current	13m 26s
Slack Notifications / Prepare notifications	4s
Compare / Multisite Default	12s
Compare / Single Site Default	17s
Compare / Single Site Memcached	17s
Compare / Multisite Memcached	8s
Slack Notifications / Success notifications	2s
Slack Notifications / Failure notifications	0s
Slack Notifications / Cancelled notifications	0s
Slack Notifications / Fixed notifications	0s
Failed workflow tasks	0s
	1h 51m 33s

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