Fix #330575: fix NPE in reActivateSession

Author: LEDfan

src/main/java/eu/openanalytics/containerproxy/service/session/redis/RedisSessionService.java

@@ -90,8 +90,10 @@ public Integer getActiveUsersCount() {
 
     @Override
     public void reActivateSession(String sessionId) {
-        Session session = redisIndexedSessionRepository.findById(sessionId);//l.setLastAccessedTime
-        session.setLastAccessedTime(Instant.now());
+        Session session = redisIndexedSessionRepository.findById(sessionId);
+        if (session != null) {
+            session.setLastAccessedTime(Instant.now());
+        }
     }
 
     @Override