core: fix warnings

src/core/dumping/ffmpeg_backend.h

@@ -37,7 +37,7 @@ public:
 protected:
     ~FFmpegStream();
 
-    void WritePacket(AVPacket& packet);
+    void WritePacket(AVPacket* packet);
     void SendFrame(AVFrame* frame);
 
     struct AVCodecContextDeleter {
@@ -52,6 +52,12 @@ protected:
         }
     };
 
+    struct AVPacketDeleter {
+        void operator()(AVPacket* packet) const {
+            av_packet_free(&packet);
+        }
+    };
+
     AVFormatContext* format_context{};
     std::mutex* format_context_mutex{};
     std::unique_ptr<AVCodecContext, AVCodecContextDeleter> codec_context{};