Add a Util.nullSafeArrayAppend and use it in HlsSampleStreamWrapper

I could do this with nullSafeArrayConcat but this saves allocating a throw-away
single-element array.

PiperOrigin-RevId: 274545815

library/core/src/main/java/com/google/android/exoplayer2/util/Util.java

@@ -336,7 +336,20 @@ public final class Util {
   }
 
   /**
-   * Concatenates two non-null type arrays.
+   * Creates a new array containing {@code original} with {@code newElement} appended.
+   *
+   * @param original The input array.
+   * @param newElement The element to append.
+   * @return The new array.
+   */
+  public static <T> T[] nullSafeArrayAppend(T[] original, T newElement) {
+    @NullableType T[] result = Arrays.copyOf(original, original.length + 1);
+    result[original.length] = newElement;
+    return castNonNullTypeArray(result);
+  }
+
+  /**
+   * Creates a new array containing the concatenation of two non-null type arrays.
    *
    * @param first The first array.
    * @param second The second array.

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsSampleStreamWrapper.java

@@ -905,11 +905,11 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
     trackOutput.setUpstreamFormatChangeListener(this);
     sampleQueueTrackIds = Arrays.copyOf(sampleQueueTrackIds, trackCount + 1);
     sampleQueueTrackIds[trackCount] = id;
-    sampleQueues = Arrays.copyOf(sampleQueues, trackCount + 1);
-    sampleQueues[trackCount] = trackOutput;
-    sampleQueueReaders = Arrays.copyOf(sampleQueueReaders, trackCount + 1);
-    sampleQueueReaders[trackCount] =
-        new DecryptableSampleQueueReader(sampleQueues[trackCount], drmSessionManager);
+    sampleQueues = Util.nullSafeArrayAppend(sampleQueues, trackOutput);
+    sampleQueueReaders =
+        Util.nullSafeArrayAppend(
+            sampleQueueReaders,
+            new DecryptableSampleQueueReader(sampleQueues[trackCount], drmSessionManager));
     sampleQueueIsAudioVideoFlags = Arrays.copyOf(sampleQueueIsAudioVideoFlags, trackCount + 1);
     sampleQueueIsAudioVideoFlags[trackCount] =
         type == C.TRACK_TYPE_AUDIO || type == C.TRACK_TYPE_VIDEO;