Tests: Add unit test for empty comment tags in export #29466

Job	Run time
Determine Matrix	4s
Single Site Memcached / Test current	13m 5s
Multisite Memcached / Test current	12m 53s
Multisite Memcached / Test before	12m 56s
Single Site Default / Test before	13m 4s
Single Site Memcached / Test before	12m 58s
Single Site Default / Test current	12m 49s
Multisite Default / Test current	13m 2s
Multisite Default / Test before	12m 53s
Compare / Multisite Memcached	24s
Compare / Single Site Memcached	15s
Compare / Single Site Default	12s
Compare / Multisite Default	13s
Failed workflow tasks	0s
Slack Notifications	0s
	1h 44m 48s

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