Coding Standards: replace isset() ternary with null coalescing #23006

Job	Run time
Determine Matrix	3s
Single Site Default / Test before	13m 39s
Single Site Memcached / Test before	14m 27s
Multisite Default / Test current	14m 42s
Multisite Default / Test before	15m 2s
Multisite Memcached / Test before	13m 41s
Multisite Memcached / Test current	14m 24s
Single Site Memcached / Test current	13m 18s
Single Site Default / Test current	13m 52s
Compare / Single Site Memcached	11s
Compare / Single Site Default	11s
Compare / Multisite Default	12s
Compare / Multisite Memcached	19s
Slack Notifications	0s
Failed workflow tasks	0s
	1h 54m 1s

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