Merge pull request #2898 from ouyangshengduo/master

修改at_socket.c文件中的sendto函数，len局部变量没有给初始值

components/net/at/at_socket/at_socket.c

@@ -856,7 +856,7 @@ int at_recv(int s, void *mem, size_t len, int flags)
 int at_sendto(int socket, const void *data, size_t size, int flags, const struct sockaddr *to, socklen_t tolen)
 {
     struct at_socket *sock = RT_NULL;
-    int len, result = 0;
+    int len = 0, result = 0;
 
     if (data == RT_NULL || size == 0)
     {