Properly access line widgets when computing coordinates in continued lines

Closes codemirror#6862

Author: marijnh

src/measurement/position_measurement.js

@@ -295,9 +295,9 @@ function pageScrollY() {
 }
 
 function widgetTopHeight(lineObj) {
- let height = 0
- if (lineObj.widgets) for (let i = 0; i < lineObj.widgets.length; ++i) if (lineObj.widgets[i].above)
- height += widgetHeight(lineObj.widgets[i])
+ let {widgets} = visualLine(lineObj), height = 0
+ if (widgets) for (let i = 0; i < widgets.length; ++i) if (widgets[i].above)
+ height += widgetHeight(widgets[i])
  return height
 }