提取特征BUG修改

nlp-web/src/main/java/org/diagbot/nlp/controller/FeatureController.java

@@ -131,6 +131,9 @@ public class FeatureController extends BaseController<Feature, FeatureWrapper, L
                             break;
                     }
                     featureList = sa.start(content, FeatureType.parse(featureType));
+                    if (featureList == null) {
+                        continue;
+                    }
                     for (int i = 0; i < featureList.size(); i++) {
                         featureMap = featureList.get(i);
                         featureMap.put("rdn", info.getRdn());