MOD: redis 提供

recommend-server-service/src/main/java/com/tzld/piaoquan/recommend/server/framework/candidiate/Queue.java

@@ -49,7 +49,7 @@ public class Queue<T> implements Iterable<Entry<T>> {
     }
 
     public void limit(int num) {
-        if (num >= 0 && num < entries.size()) {
+        if (!entries.isEmpty() && num >= 0 && num < entries.size()) {
             entries.subList(num, entries.size()).clear();
         }
     }