Fix NPE in `ServiceConfigurations` resource by handling missing `Account` #2581

Job	Run time
Build	5m 29s
test-connection	14m 29s
test-broker	27m 2s
test-brokerAcl	17m 24s
test-datastore	15m 17s
test-device-management	12m 21s
test-tag	2m 40s
test-userIntegrationBase	7m 26s
test-user	4m 0s
test-accountAndTranslator	6m 28s
test-jobEngineStepDefinitions	7m 47s
test-device	4m 43s
test-jobsAndScheduler	2m 47s
test-jobsIntegration	9m 31s
test-jobsIntegrationBase	9m 49s
test-security	5m 26s
test-userIntegration	8m 15s
build-javadoc	10m 6s
junit-tests	8m 38s
test-api-auth	7m 10s
test-deviceRegistry	12m 43s
test-endpoint	8m 8s
test-jobEngineRestartOfflineDevice	9m 52s
test-jobEngineRestartOnlineDevice	11m 4s
test-jobEngineRestartOnlineDeviceSecondPart	10m 36s
test-jobEngineServiceStop	14m 5s
test-jobEngineStartOfflineDevice	10m 37s
test-jobEngineStartOnlineDevice	12m 42s
test-RoleAndGroup	2m 49s
test-api-corsfilter	6m 46s
	4h 46m 10s

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