Fix Spider main thread any problem with redis connection (when working with redis-based schedulers) leads to unhandled exception and release the main (control) thread

[Interfer0n]

Exception in thread "Thread-5" redis.clients.jedis.exceptions.JedisConnectionException: Unexpected end of stream.
    at redis.clients.util.RedisInputStream.ensureFill(RedisInputStream.java:199)
    at redis.clients.util.RedisInputStream.readByte(RedisInputStream.java:40)
    at redis.clients.jedis.Protocol.process(Protocol.java:151)
    at redis.clients.jedis.Protocol.read(Protocol.java:215)
    at redis.clients.jedis.Connection.readProtocolWithCheckingBroken(Connection.java:340)
    at redis.clients.jedis.Connection.getStatusCodeReply(Connection.java:239)
    at redis.clients.jedis.BinaryJedis.select(BinaryJedis.java:523)
    at us.codecraft.webmagic.scheduler.RedisPriorityScheduler.poll(RedisPriorityScheduler.java:63)
    at us.codecraft.webmagic.Spider.run(Spider.java:309)
    at java.lang.Thread.run(Thread.java:748)