Fix: Optimize the update logic of the default size of the `Sprite`

[cptbtptpbcptdtptp]

When replacing textures or modifying regions, the sprite size should be updated.

Before:

sprite.texture = oldTexture;
// sprite.region = oldRegion;
console.log('old width',  sprite.width);
sprite.texture = newTexture;
// sprite.region = newRegion;
console.log('new width',  sprite.width);

The results obtained are equal.

But we think that at this moment the developer wants to update the width and height of the sprite.