Why does RH-SSO throw a NullPointerException when I try to export a realm?

Issue

• Trying to only export one realm (excluding the master) to a directory with the following command:
  ./bin/standalone.sh -Dkeycloak.migration.action=export -Dkeycloak.migration.provider=dir -Dkeycloak.migration.realmName=NotMaster -Dkeycloak.migration.dir=example.realm

No JSON export file is created. The output is below:

08:26:15,322 INFO  [org.keycloak.services] (ServerService Thread Pool -- 48) KC-SERVICES0034: Export of realm 'NotMaster' requested.
08:26:15,340 ERROR [org.jboss.msc.service.fail] (ServerService Thread Pool -- 48) MSC000001: Failed to start service jboss.undertow.deployment.default-server.default-host./auth: org.jboss.msc.service.StartException in service jboss.undertow.deployment.default-server.default-host./auth: java.lang.RuntimeException: RESTEASY003325: Failed to construct public org.keycloak.services.resources.KeycloakApplication(javax.servlet.ServletContext,org.jboss.resteasy.core.Dispatcher)
        at org.wildfly.extension.undertow.deployment.UndertowDeploymentService$1.run(UndertowDeploymentService.java:85)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:745)
        at org.jboss.threads.JBossThread.run(JBossThread.java:320)
Caused by: java.lang.RuntimeException: RESTEASY003325: Failed to construct public org.keycloak.services.resources.KeycloakApplication(javax.servlet.ServletContext,org.jboss.resteasy.core.Dispatcher)
        at org.jboss.resteasy.core.ConstructorInjectorImpl.construct(ConstructorInjectorImpl.java:162)
        at org.jboss.resteasy.spi.ResteasyProviderFactory.createProviderInstance(ResteasyProviderFactory.java:2209)
        at org.jboss.resteasy.spi.ResteasyDeployment.createApplication(ResteasyDeployment.java:299)
        at org.jboss.resteasy.spi.ResteasyDeployment.start(ResteasyDeployment.java:240)
        at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.init(ServletContainerDispatcher.java:113)
        at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.init(HttpServletDispatcher.java:36)
        at io.undertow.servlet.core.LifecyleInterceptorInvocation.proceed(LifecyleInterceptorInvocation.java:117)
        at org.wildfly.extension.undertow.security.RunAsLifecycleInterceptor.init(RunAsLifecycleInterceptor.java:78)
        at io.undertow.servlet.core.LifecyleInterceptorInvocation.proceed(LifecyleInterceptorInvocation.java:103)
        at io.undertow.servlet.core.ManagedServlet$DefaultInstanceStrategy.start(ManagedServlet.java:239)
        at io.undertow.servlet.core.ManagedServlet.createServlet(ManagedServlet.java:133)
        at io.undertow.servlet.core.DeploymentManagerImpl.start(DeploymentManagerImpl.java:527)
        at org.wildfly.extension.undertow.deployment.UndertowDeploymentService.startContext(UndertowDeploymentService.java:101)
        at org.wildfly.extension.undertow.deployment.UndertowDeploymentService$1.run(UndertowDeploymentService.java:82)
        ... 6 more
Caused by: java.lang.NullPointerException
        at org.keycloak.models.utils.ModelToRepresentation.toRepresentation(ModelToRepresentation.java:226)
        at org.keycloak.exportimport.util.ExportUtils.exportRealm(ExportUtils.java:41)
        at org.keycloak.exportimport.util.MultipleStepsExportProvider$2.runExportImportTask(MultipleStepsExportProvider.java:77)
        at org.keycloak.exportimport.util.ExportImportSessionTask.run(ExportImportSessionTask.java:35)
        at org.keycloak.models.utils.KeycloakModelUtils.runJobInTransaction(KeycloakModelUtils.java:287)
        at org.keycloak.exportimport.util.MultipleStepsExportProvider.exportRealmImpl(MultipleStepsExportProvider.java:72)
        at org.keycloak.exportimport.util.MultipleStepsExportProvider.exportRealm(MultipleStepsExportProvider.java:63)
        at org.keycloak.exportimport.ExportImportManager.runExport(ExportImportManager.java:104)
        at org.keycloak.services.resources.KeycloakApplication.<init>(KeycloakApplication.java:140)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
        at org.jboss.resteasy.core.ConstructorInjectorImpl.construct(ConstructorInjectorImpl.java:150)
        ... 19 more