Fix NPE in `ServiceConfigurations` resource by handling missing `Account` #2580

Job	Run time
Build	5m 27s
test-broker	26m 44s
test-tag	2m 30s
test-brokerAcl	17m 23s
test-connection	13m 59s
test-datastore	15m 31s
test-device	5m 6s
test-device-management	13m 40s
test-userIntegrationBase	7m 45s
test-user	3m 45s
test-accountAndTranslator	6m 11s
test-jobEngineRestartOfflineDevice	10m 29s
test-jobEngineRestartOnlineDevice	12m 24s
test-jobEngineStartOfflineDevice	11m 11s
test-jobEngineStartOnlineDevice	13m 9s
test-jobEngineStepDefinitions	8m 25s
test-jobsAndScheduler	2m 49s
test-jobsIntegration	9m 30s
test-jobsIntegrationBase	9m 39s
test-security	5m 22s
test-userIntegration	8m 8s
build-javadoc	10m 48s
junit-tests	8m 47s
test-api-auth	7m 8s
test-deviceRegistry	12m 14s
test-endpoint	7m 54s
test-jobEngineRestartOnlineDeviceSecondPart	12m 54s
test-jobEngineServiceStop	14m 38s
test-RoleAndGroup	2m 45s
test-api-corsfilter	6m 52s
	4h 53m 7s

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