Do not close NowPlayingBottomSheet between tracks.

If the user opens the NowPlayingBottomSheet whilst playing a non empty queue, leave the BottomSheet open at the end of the playing track.

This is meant to address the first issue in the list of UI rough edges identified in issue #155.

app/src/main/java/audio/funkwhale/ffa/views/NowPlayingBottomSheet.kt

@@ -74,7 +74,9 @@ class NowPlayingBottomSheet @JvmOverloads constructor(
 
   override fun show() {
     behavior.isHideable = false
-    close()
+    if (behavior.state == BottomSheetBehavior.STATE_HIDDEN) {
+      close()
+    }
   }
 
   override fun hide() {