Ensure empty plugin settings are saved correctly (#22885) #7316

Job	Run time
Javascript	3m 20s
UI (0)	34m 17s
Client	1m 18s
UI (1)	16m 39s
PHP (UnitTests, 7.2, Mysql, PDO_MYSQL)	2m 44s
UI (2)	17m 35s
PHP (UnitTests, 8.2, Mariadb, PDO_MYSQL)	2m 42s
UI (3)	14m 38s
PHP (UnitTests, 8.4, Mysql, MYSQLI)	2m 48s
PHP (SystemTestsPlugins, 7.2, Mysql, PDO_MYSQL)	13m 51s
PHP (SystemTestsPlugins, 8.2, Mariadb, PDO_MYSQL)	12m 52s
PHP (SystemTestsPlugins, 8.4, Mysql, MYSQLI)	17m 15s
PHP (SystemTestsCore, 7.2, Mysql, PDO_MYSQL)	10m 3s
PHP (SystemTestsCore, 8.2, Mariadb, PDO_MYSQL)	8m 50s
PHP (SystemTestsCore, 8.4, Mysql, MYSQLI)	9m 24s
PHP (IntegrationTestsCore, 7.2, Mysql, PDO_MYSQL)	14m 0s
PHP (IntegrationTestsCore, 8.2, Mariadb, PDO_MYSQL)	12m 28s
PHP (IntegrationTestsCore, 8.4, Mysql, MYSQLI)	15m 32s
PHP (IntegrationTestsPlugins, 7.2, Mysql, PDO_MYSQL)	33m 27s
PHP (IntegrationTestsPlugins, 8.2, Mariadb, PDO_MYSQL)	30m 34s
PHP (IntegrationTestsPlugins, 8.4, Mysql, MYSQLI)	40m 32s
	5h 14m 49s

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