Fix bug where it was impossible to remove member or pool if class above (pool...

Fix bug where it was impossible to remove member or pool if class above (pool for members and vip for pools)  was removed before.

src/main/java/net/floodlightcontroller/loadbalancer/LoadBalancer.java

@@ -687,7 +687,7 @@ public class LoadBalancer implements IFloodlightModule,
             pool = pools.get(poolId);
             if (pool == null)	// fix dereference violations
             	return -1;
-            if (pool.vipId != null)
+            if (pool.vipId != null && vips.containsKey(pool.vipId))
                 vips.get(pool.vipId).pools.remove(poolId);
             pools.remove(poolId);
             return 0;
@@ -750,7 +750,7 @@ public class LoadBalancer implements IFloodlightModule,
         member = members.get(memberId);
         
         if(member != null){
-            if (member.poolId != null)
+            if (member.poolId != null && pools.containsKey(member.poolId))
                 pools.get(member.poolId).members.remove(memberId);
             members.remove(memberId);
             return 0;