fix(jans): add null check to avoid NullPointerException

[pujavs]

Describe the bug
Getting NullPointerException is two cases
1) CustomObjectAttribute:
URL: GET https://jenkins-build.jans.io/jans-config-api/mgt/configuser?limit=3
Logs:
config-api-CustomObjectAttribute-6028.log

Log snippet:
Caused by: java.lang.NullPointerException at io.jans.orm.model.base.CustomObjectAttribute.getDisplayValue(CustomObjectAttribute.java:92) at jdk.internal.reflect.GeneratedMethodAccessor1136.invoke(Unknown Source) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:566) at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:689) at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:774)

Screenshot:

2) LocalizedString

URL: POST http://localhost:8080/jans-config-api/api/v1/openid/clients
JSON:
{ "dn": null, "expirationDate": null, "deletable": true, "clientSecret": "password", "frontChannelLogoutUri": null, "frontChannelLogoutSessionRequired": true, "registrationAccessToken": null, "clientIdIssuedAt": null, "clientSecretExpiresAt": null, "redirectUris": ["https://myserver.com"], "claimRedirectUris": [], "responseTypes": [], "grantTypes": [], "applicationType": "native", "contacts": [], "idTokenTokenBindingCnf": null, "clientName": "clientName-test1", "logoUri": null, "clientUri": null, "policyUri": null, "tosUri": null, "clientNameLocalized": { "values": null, "value": null, "languageTags": [] }, "logoUriLocalized": { "values": null, "value": "https://myserver.com/logoUriLocalized", "languageTags": [] }, "clientUriLocalized": { "values": null, "value": "https://myserver.com/clientUriLocalized", "languageTags": [] }, "policyUriLocalized": { "values": null, "value": "https://myserver.com/policyUriLocalized", "languageTags": [] }, "tosUriLocalized": { "values": null, "value": "https://myserver.com/tosUriLocalized", "languageTags": [] }, "jwksUri": null, "jwks": null, "sectorIdentifierUri": null, "subjectType": "public", "idTokenSignedResponseAlg": null, "idTokenEncryptedResponseAlg": null, "idTokenEncryptedResponseEnc": null, "userInfoSignedResponseAlg": null, "userInfoEncryptedResponseAlg": null, "userInfoEncryptedResponseEnc": null, "requestObjectSigningAlg": null, "requestObjectEncryptionAlg": null, "requestObjectEncryptionEnc": null, "tokenEndpointAuthMethod": null, "tokenEndpointAuthSigningAlg": null, "defaultMaxAge": null, "defaultAcrValues": [], "initiateLoginUri": null, "postLogoutRedirectUris": [], "requestUris": [], "scopes": [], "claims": [], "trustedClient": true, "lastAccessTime": null, "lastLogonTime": null, "persistClientAuthorizations": true, "includeClaimsInIdToken": true, "refreshTokenLifetime": null, "accessTokenLifetime": null, "customAttributes": [{ "name": "displayName", "multiValued": false, "values": ["Jans Role Based Client"], "value": "Jans Role Based Client", "displayValue": "Jans Role Based Client" }], "customObjectClasses": [], "rptAsJwt": true, "accessTokenAsJwt": true, "accessTokenSigningAlg": null, "disabled": true, "authorizedOrigins": [], "softwareId": null, "softwareVersion": null, "softwareStatement": null, "attributes": { "tlsClientAuthSubjectDn": null, "runIntrospectionScriptBeforeJwtCreation": false, "keepClientAuthorizationAfterExpiration": true, "allowSpontaneousScopes": true, "spontaneousScopes": [], "spontaneousScopeScriptDns": [], "updateTokenScriptDns": [], "backchannelLogoutUri": [], "backchannelLogoutSessionRequired": true, "additionalAudience": [], "postAuthnScripts": [], "consentGatheringScripts": [], "introspectionScripts": [], "rptClaimsScripts": [], "ropcScripts": [], "parLifetime": null, "requirePar": false, "jansAuthSignedRespAlg": null, "jansAuthEncRespAlg": null, "jansAuthEncRespEnc": null, "jansSubAttr": null, "redirectUrisRegex": null, "jansAuthorizedAcr": [], "jansDefaultPromptLogin": true, "idTokenLifetime": null }, "backchannelTokenDeliveryMode": "poll", "backchannelClientNotificationEndpoint": null, "backchannelAuthenticationRequestSigningAlg": "PS384", "backchannelUserCodeParameter": true, "description": null, "organization": null, "groups": [], "ttl": null, "displayName": null, "tokenBindingSupported": false, "authenticationMethod": "client_secret_jwt", "baseDn": null, "inum": null }

Logs:
config-api-LocalizedString-2022_11_24.jetty.log

Log snippet:
Caused by: java.lang.NullPointerException at io.jans.orm.model.base.LocalizedString.getLanguageTags(LocalizedString.java:77) at io.jans.orm.ldap.impl.LdapEntryManager.getAttributeDataListFromLocalizedString(LdapEntryManager.java:641) at io.jans.orm.ldap.impl.LdapEntryManager.addAttributeDataFromLocalizedString(LdapEntryManager.java:995) at io.jans.orm.impl.BaseEntryManager.getAttributesListForPersist(BaseEntryManager.java:1574) at io.jans.orm.impl.BaseEntryManager.persist(BaseEntryManager.java:107) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:566)

Screenshot: