Add return in deleteTask

Summary:
If taskInfo is null , we should do return after sending the response.
Else we will get exception when trying to read the null taskinfo

Reviewed By: shangm2

Differential Revision: D80284931

Author: NikhilCollooru

presto-native-execution/presto_cpp/main/TaskResource.cpp

@@ -415,6 +415,7 @@ proxygen::RequestHandler* TaskResource::deleteTask(
               if (!handlerState->requestExpired()) {
                 if (taskInfo == nullptr) {
                   sendTaskNotFound(downstream, taskId);
+                  return;
                 }
                 if (sendThrift) {
                   thrift::TaskInfo thriftTaskInfo;