[video_player] Future already completed fix

[Yarikk26]

Workaround for flutter/flutter#19197.
Checked on the video from example project and on my use-cases.

[cbenhagen]

I don't think this is an appropriate fix as playbackLikelyToKeepUp has nothing to do with being initialized.

Either we make sure to only send the initialized event once from the iOS side. Or we do this in dart:

if (!value.initialized) {
  value = value.copyWith(
    duration: Duration(milliseconds: map['duration']),
    size: Size(map['width']?.toDouble() ?? 0.0,
        map['height']?.toDouble() ?? 0.0),
  );
  initializingCompleter.complete(null);
  _applyLooping();
  _applyVolume();
  _applyPlayPause();
}

[iskakaushik]

This should be addressed in version: 0.10.0+8 by this PR: #1552 please re-open this if it's still an issue. Thanks!