fix: compute the current style of ShadowRoot element (#214)

`ShadowRoot` element cannot be passed to the `window.getComputedStyle`
method.
Otherwise, errors occur, in particular, it prevents the mouse and
gesture events to be propagated.

packages/core/src/util/styleUtils.ts

@@ -56,14 +56,12 @@ export const removeCursors = (element: HTMLElement) => {
 };
 
 /**
- * Function: getCurrentStyle
- *
  * Returns the current style of the specified element.
  *
  * @param element DOM node whose current style should be returned.
  */
 export const getCurrentStyle = (element: HTMLElement) => {
-  return element ? window.getComputedStyle(element, '') : null;
+  return !element || element.toString() === '[object ShadowRoot]' ? null : window.getComputedStyle(element, '');
 };
 
 /**