MediaWrapperList: fix isAudioList

replaceWith and Map didn't update videoCount, causing it's value to be
wrong most of the time, breaking isAudioList

application/vlc-android/src/org/videolan/vlc/media/MediaWrapperList.kt

@@ -160,11 +160,13 @@ class MediaWrapperList {
     fun replaceWith(list: List<MediaWrapper>) {
         internalList.clear()
         internalList.addAll(list)
+        videoCount = internalList.count { it.type == MediaWrapper.TYPE_VIDEO }
     }
 
     @Synchronized
     fun map(list: List<MediaWrapper>) {
         internalList.addAll(list)
+        videoCount = internalList.count { it.type == MediaWrapper.TYPE_VIDEO }
     }
 
     /**