modify YamlTableRuleConfiguration.java

sharding-core/src/main/java/io/shardingsphere/core/yaml/sharding/YamlTableRuleConfiguration.java

@@ -43,7 +43,7 @@ public class YamlTableRuleConfiguration {
     
     private YamlShardingStrategyConfiguration tableStrategy;
     
-    private YamlKeyGeneratorConfiguration keyGenerator;
+    private YamlKeyGeneratorConfiguration keyGenerator = new YamlKeyGeneratorConfiguration();
     
     private String logicIndex;