Media: Account for boolean false being returned by `wp_getimagesize()… #22863

Job	Run time
Core running from src / MacOS	2m 52s
Core running from build / MacOS	3m 48s
Core running from build / Windows	4m 28s
Core running from src / Windows	4m 6s
Core running from src / Linux	2m 22s
Core running from build / Linux	2m 30s
Gutenberg running from src / Linux	8m 28s
Gutenberg running from build / MacOS	14m 13s
Gutenberg running from build / Linux	8m 48s
Gutenberg running from src / MacOS	8m 56s
Gutenberg running from src / Windows	13m 9s
Gutenberg running from build / Windows	13m 5s
Slack Notifications / Prepare notifications	3s
Slack Notifications / Success notifications	5s
Slack Notifications / Fixed notifications	0s
Slack Notifications / Cancelled notifications	0s
Slack Notifications / Failure notifications	0s
Failed workflow tasks	0s
	1h 26m 53s

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