minimap：在给minimap传递options之后 小地图中的viewport更新不及时

在不传递options之前 拖动和缩放画布，小地图的功能正常，但凡传递一个options即使这个options只是个空对象，也会导致拖动和缩放画布之后viewport蓝色框消失（去小地图画布左上角了，如下图），只有再次滑动鼠标到元素上才可以重新渲染出来viewport蓝色框。

Start by reproducing the minimap behavior with an empty options object, then compare it with the default configuration while dragging and zooming the canvas. Done means the blue viewport box stays correctly positioned and updates immediately after those interactions without requiring the pointer to move over an element.

Written by the indexing model from the issue text.