refactor: improve the accuracy of docs/improve docs (#4845)

Co-authored-by: Noel <icrawltogo@gmail.com>

src/client/voice/VoiceConnection.js

@@ -165,7 +165,7 @@ class VoiceConnection extends EventEmitter {
 
   /**
    * The voice state of this connection
-   * @type {VoiceState}
+   * @type {?VoiceState}
    */
   get voice() {
     return this.channel.guild.voice;
@@ -203,8 +203,8 @@ class VoiceConnection extends EventEmitter {
    * Set the token and endpoint required to connect to the voice servers.
    * @param {string} token The voice token
    * @param {string} endpoint The voice endpoint
-   * @private
    * @returns {void}
+   * @private
    */
   setTokenAndEndpoint(token, endpoint) {
     this.emit('debug', `Token "${token}" and endpoint "${endpoint}"`);

src/client/voice/dispatcher/StreamDispatcher.js

@@ -56,7 +56,7 @@ class StreamDispatcher extends Writable {
      * The broadcast controlling this dispatcher, if any
      * @type {?VoiceBroadcast}
      */
-    this.broadcast = this.streams.broadcast;
+    this.broadcast = this.streams.broadcast || null;
 
     this._pausedTime = 0;
     this._silentPausedTime = 0;