Fix null issue in url youtube url when running a playlist with no videoId

When playing a playlist via playerVars.list = [playlistId] we dont have a videoId available yet. Plus we don't need one, Youtube will start at the first video of the playlist by default.

By injecting an undefined videoId in the YT Player constructur, we end up with null value in the iframe url (`ps://www.youtube.com/embed/null?cc_load_policy=1&enablejsapi=1&controls=1&showinfo=0&rel=0&listType=playlist&list=PLxf07yK_HAvdwhW-L0X3uP5aMe6eEt50v`) which is causing an Invalid Video Id error for consumers.

Author: mattiLeBlanc

src/youtube-player/youtube-player.ts

@@ -587,17 +587,21 @@ export class YouTubePlayer implements AfterViewInit, OnChanges, OnDestroy {
 
     // Important! We need to create the Player object outside of the `NgZone`, because it kicks
     // off a 250ms setInterval which will continually trigger change detection if we don't.
+    const params: any = {
+      host: this.disableCookies ? 'https://www.youtube-nocookie.com' : undefined,
+      width: this.width,
+      height: this.height,
+      // Calling `playVideo` on load doesn't appear to actually play
+      // the video so we need to trigger it through `playerVars` instead.
+      playerVars: playVideo ? {...(this.playerVars || {}), autoplay: 1} : this.playerVars,
+    }
+    // We only want to injecct a videoId if one is provided, otherwise loading a playlist via playerVars.list, the missing videoId will create a null value in the youtube iframe url and that can trigger a JS error `Invalid video id` in widget api.
+    if (this.videoId) {
+      params.videoId = this.videoId;
+    }
     const player = this._ngZone.runOutsideAngular(
       () =>
-        new YT.Player(this.youtubeContainer.nativeElement, {
-          videoId: this.videoId,
-          host: this.disableCookies ? 'https://www.youtube-nocookie.com' : undefined,
-          width: this.width,
-          height: this.height,
-          // Calling `playVideo` on load doesn't appear to actually play
-          // the video so we need to trigger it through `playerVars` instead.
-          playerVars: playVideo ? {...(this.playerVars || {}), autoplay: 1} : this.playerVars,
-        }),
+        new YT.Player(this.youtubeContainer.nativeElement, params),
     );
 
     const whenReady = (event: YT.PlayerEvent) => {