playback: fix improper re-initializaiton

Fix issues stemming from how ExoPlayer apparently doesn't send a
playWhenReady event after being stopped.

This ended up breaking AudioEffect integration and notification
posting. I really don't know why player.stop() doesn't do this.

CHANGELOG.md

@@ -22,7 +22,7 @@ within it
 - Fixed freezing occuring when scrolling through large music libraries
 - Fixed app not responding once music loading completes for large libraries
 - Fixed crash when the last song of the queue gets removed while playing
-- Fixed playback UI not re-appearing after playback ends
+- Fixed playback UI and notification not re-appearing after playback ends
 
 #### What's Changed
 - Android Lollipop and Marshmallow support have been dropped

app/src/main/java/org/oxycblt/auxio/playback/system/PlaybackService.kt

@@ -226,8 +226,11 @@ class PlaybackService :
         if (song == null) {
             // No song, stop playback and foreground state.
             logD("Nothing playing, stopping playback")
+            // For some reason the player does not mark playWhenReady as false when stopped,
+            // which then completely breaks any re-initialization if playback starts again.
+            // So we manually set it to false here.
+            player.playWhenReady = false
             player.stop()
-
             stopAndSave()
             return
         }