Possible NPE in SubjectImpl#hasApplication when site has been stopped

log4j: 2020-09-09 14:25:27,578 ERROR ["http-nio-8080-exec-2"] [ 52AB5AF8E020C58268CAED3672518FF6 "m989@de"  /manager/appng-manager] model.PlatformProcessor: error while processing
java.lang.NullPointerException
        at org.appng.core.domain.SubjectImpl.hasApplication(SubjectImpl.java:198)
        at org.appng.core.model.NavigationBuilder.addSiteNavigation(NavigationBuilder.java:227)
        at org.appng.core.model.NavigationBuilder.processSiteTemplate(NavigationBuilder.java:164)
        at org.appng.core.model.NavigationBuilder.processNavigation(NavigationBuilder.java:85)
        at org.appng.core.model.AbstractRequestProcessor.processPlatform(AbstractRequestProcessor.java:182)
        at org.appng.core.model.PlatformProcessor.processWithTemplate(PlatformProcessor.java:92)
        at org.appng.core.controller.handler.GuiHandler.processGui(GuiHandler.java:189)
        at org.appng.core.controller.handler.GuiHandler.handle(GuiHandler.java:84)
        at org.appng.core.controller.Controller.doGet(Controller.java:264)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:626)