fix null pointer

server/src/main/java/org/apache/iotdb/db/engine/cache/TimeSeriesMetadataCache.java

@@ -160,7 +160,11 @@ public class TimeSeriesMetadataCache {
         }
       }
     }
-    return new TimeseriesMetadata(timeseriesMetadata);
+    if (timeseriesMetadata == null) {
+      return null;
+    } else {
+      return new TimeseriesMetadata(timeseriesMetadata);
+    }
   }
 
 

server/src/main/java/org/apache/iotdb/db/service/TSServiceImpl.java

@@ -633,6 +633,9 @@ public class TSServiceImpl implements TSIService.Iface, ServerContext {
       return resp;
     } catch (Exception e) {
       logger.error("{}: Internal server error: ", IoTDBConstant.GLOBAL_DB_NAME, e);
+      if (e instanceof NullPointerException) {
+        e.printStackTrace();
+      }
       if (queryId != -1) {
         try {
           releaseQueryResource(queryId);