Fix raise on nil start time

Author: sgfn

lib/ex_webrtc_recorder/converter.ex

@@ -232,6 +232,8 @@ defmodule ExWebRTC.Recorder.Converter do
       end)
 
     # FIXME: This won't work if we have audio/video only
+    IO.inspect(stream_map, label: :STREAM_MAP_IS)
+
     for {stream_id, %{video: video_files, audio: audio_files}} <- stream_map,
         {rid, %{filename: video_file, start_time: video_start}} <- video_files,
         {nil, %{filename: audio_file, start_time: audio_start}} <- audio_files,

lib/ex_webrtc_recorder/converter/ffmpeg.ex

@@ -50,6 +50,11 @@ defmodule ExWebRTC.Recorder.Converter.FFmpeg do
     round(duration_seconds)
   end
 
+  defp calculate_start_times(video_start_ms, audio_start_ms)
+       when is_nil(video_start_ms) or is_nil(audio_start_ms) do
+    {"00:00:00.000", "00:00:00.000"}
+  end
+
   defp calculate_start_times(video_start_ms, audio_start_ms) do
     diff = abs(video_start_ms - audio_start_ms)
     s = div(diff, 1000)