CustomPiP: fix popup killed when leaving the app

When leaving the app with custom pip the VideoPlayerActivity onStop()
is called which sets isInPiPMode to false which kills the popup.
onStop isn't called with the system's pip.
To fix this, just check if service.isPlayingPopup is true, it's false
for system's pip.

application/vlc-android/src/org/videolan/vlc/gui/video/PopupManager.kt

@@ -84,6 +84,9 @@ class PopupManager constructor(private val service: PlaybackService) : PlaybackS
 
     fun removePopup() {
         service.isInPiPMode.removeObserver(observer)
+        // If the popup is killed from the x button, isInPiPMode will still be true
+        // and when reopening the app will restart the video player
+        service.isInPiPMode.value = false
         hideNotification()
         val view = rootView ?: return
         service.removeCallback(this)

application/vlc-android/src/org/videolan/vlc/gui/video/VideoPlayerActivity.kt

@@ -959,7 +959,8 @@ open class VideoPlayerActivity : AppCompatActivity(), PlaybackService.Callback,
         cleanUI()
         stopPlayback()
         service?.playlistManager?.videoStatsOn?.postValue(false)
-        if (isInteractive)
+        val isPlayingPopup = service?.isPlayingPopup ?: false
+        if (isInteractive && !isPlayingPopup)
             service?.isInPiPMode?.value = false
 
         if (savedTime != -1L) settings.putSingle(VIDEO_RESUME_TIME, savedTime)