Fix updating playing status

Model/Player/Backends/MPVBackend.swift

@@ -366,6 +366,7 @@ final class MPVBackend: PlayerBackend {
     }
 
     private func updateControlsIsPlaying() {
+        guard model.activeBackend == .mpv else { return }
         DispatchQueue.main.async { [weak self] in
             self?.controls?.isPlaying = self?.isPlaying ?? false
         }