


Q: Given the following code slice:
```
1 void ff_rtsp_close_streams(AVFormatContext *s)
3     RTSPState *rt = s->priv_data;
4     int i;
5     RTSPStream *rtsp_st;
6     ff_rtsp_undo_setup(s);
7     for (i = 0; i < rt->nb_rtsp_streams; i++)
9         rtsp_st = rt->rtsp_streams[i];
10         if (rtsp_st)
12             if (rtsp_st->dynamic_handler && rtsp_st->dynamic_protocol_context)
14                 rtsp_st->dynamic_handler->close(rtsp_st->dynamic_protocol_context);
18     av_free(rt->rtsp_streams);
19     if (rt->asf_ctx)
21         av_close_input_stream(rt->asf_ctx);
22         rt->asf_ctx = NULL;
24     av_free(rt->p);
25     av_free(rt->recvbuf);```
which has a CWE-457 vulnerability at line:
```
16         }
```
Please generate the patch for the vulnerability. Please follow the patch format in the exemplars.
The patching can be done in two steps.

Step 1. Root Cause Analysis: The given code snippet is a function `ff_rtsp_close_streams` that is responsible for closing and cleaning up resources associated with RTSP streams. The vulnerability CWE-401 (Improper Release of Memory) exists because the memory allocated for `RTSPStream` objects (`rtsp_st`) is not properly freed before the function exits.

In the code, `rtsp_st` is a pointer to a dynamically allocated `RTSPStream` object. The code checks if `rtsp_st` is not NULL (line 10) and if it has a dynamic protocol context (line 12). If the dynamic protocol context exists, it is closed (line 14). However, the memory allocated for `rtsp_st` itself is never freed, leading to a memory leak.

Step 2. Fixing Strategy: To fix the memory leak, the patch needs to ensure that the memory allocated for each `RTSPStream` object (`rtsp_st`) is properly freed before the function exits. This can be done by adding a call to `av_free(rtsp_st)` after the dynamic protocol context is closed (if it exists) or immediately after the check for `rtsp_st` being non-NULL.

The patch adds the following lines of code:

```
<             }
<         }
---
>             }
>             av_free(rtsp_st);
>         }
```

This ensures that the memory allocated for each `RTSPStream` object (`rtsp_st`) is properly freed, resolving the CWE-401 (Improper Release of Memory) vulnerability.