Destroy audio stream when a user disconnects

src/Discord.Net.WebSocket/DiscordSocketClient.cs

@@ -1440,7 +1440,7 @@ namespace Discord.WebSocket
                                         }
                                         else
                                         {
-                                            before = guild.RemoveVoiceState(data.UserId) ?? SocketVoiceState.Default;
+                                            before = await guild.RemoveVoiceStateAsync(data.UserId).ConfigureAwait(false) ?? SocketVoiceState.Default;
                                             after = SocketVoiceState.Create(null, data);
                                         }
 

src/Discord.Net.WebSocket/Entities/Guilds/SocketGuild.cs

@@ -471,11 +471,15 @@ namespace Discord.WebSocket
                 return voiceState;
             return null;
         }
-        internal SocketVoiceState? RemoveVoiceState(ulong id)
+        internal async Task<SocketVoiceState?> RemoveVoiceStateAsync(ulong id)
         {
             SocketVoiceState voiceState;
             if (_voiceStates.TryRemove(id, out voiceState))
+            {
+                if (_audioClient != null)
+                    await _audioClient.RemoveInputStreamAsync(id).ConfigureAwait(false); //User changed channels, end their stream
                 return voiceState;
+            }
             return null;
         }