Add null check to `ExoPlayerImpl.isTunnelingEnabled`

`TrackSelectorResult.rendererConfigurations` can contain null elements:
> A null entry indicates the corresponding renderer should be disabled.

This wasn't caught by the nullness checker because `ExoPlayerImpl` is
currently excluded from analysis.

#minor-release

Issue: google/ExoPlayer#10977
PiperOrigin-RevId: 508619169

RELEASENOTES.md

@@ -35,6 +35,8 @@
         parsing trak atoms.
     *   Correctly skip samples when seeking directly to a sync frame in fMP4
         ([#10941](https://github.com/google/ExoPlayer/issues/10941)).
+    *   Fix `NullPointerException` when calling `ExoPlayer.isTunnelingEnabled`
+        ([#10977](https://github.com/google/ExoPlayer/issues/10977)).
 *   Audio:
     *   Use the compressed audio format bitrate to calculate the min buffer size
         for `AudioTrack` in direct playbacks (passthrough).

libraries/exoplayer/src/main/java/androidx/media3/exoplayer/ExoPlayerImpl.java

@@ -1725,8 +1725,9 @@ import java.util.concurrent.TimeoutException;
   @Override
   public boolean isTunnelingEnabled() {
     verifyApplicationThread();
-    for (RendererConfiguration config : playbackInfo.trackSelectorResult.rendererConfigurations) {
-      if (config.tunneling) {
+    for (@Nullable
+    RendererConfiguration config : playbackInfo.trackSelectorResult.rendererConfigurations) {
+      if (config != null && config.tunneling) {
         return true;
       }
     }