set pp attributes when exporting to public pool

src/main/java/de/thm/arsnova/services/SessionService.java

@@ -414,6 +414,7 @@ public class SessionService implements ISessionService, ApplicationEventPublishe
 	@PreAuthorize("isAuthenticated() and hasPermission(#sessionkey, 'session', 'owner')")
 	public SessionInfo copySessionToPublicPool(String sessionkey, de.thm.arsnova.entities.transport.ImportExportSession.PublicPool pp) {
 		ImportExportSession temp = databaseDao.exportSession(sessionkey, false, false);
+		temp.getSession().setPublicPool(pp);
 		temp.getSession().setSessionType("public_pool");
 		final User user = userService.getCurrentUser();
 		return databaseDao.importSession(user, temp);