Fix voice note player crash in Android 4.4

app/src/main/res/layout/voice_note_player_stub.xml

@@ -2,4 +2,4 @@
 <org.thoughtcrime.securesms.components.voice.VoiceNotePlayerView xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
-    android:background="@drawable/selectable_background" />
+    android:background="?selectableItemBackground" />