avformat/rtsp: Don't free uninitialized AVBPrint

Fixes Coverity ID 1462307.

Reviewed-by: Marton Balint <cus@passwd.hu>
Reviewed-by: Ross Nicholson <phunkyfish@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
diff --git a/libavformat/rtsp.c b/libavformat/rtsp.c
index 49f7644..0a64620 100644
--- a/libavformat/rtsp.c
+++ b/libavformat/rtsp.c
@@ -2567,8 +2567,8 @@
 fail_nobuf:
     ret = AVERROR(ENOMEM);
     av_log(s, AV_LOG_ERROR, "rtp_read_header(): not enough buffer space for sdp-headers\n");
-fail:
     av_bprint_finalize(&sdp, NULL);
+fail:
     avcodec_parameters_free(&par);
     if (in)
         ffurl_close(in);