Cannot assign to read only property 'currentTarget' of object '#<MouseEvent>'

[WeijianXu]

I got this error message when I used webpack2 to pack my code include x-tag. The detail is:
return i.stack = function(e) { e.currentTarget = e.currentTarget || this; var t = e.detail || {}; return t.__stack__ ? t.__stack__ == a ? (e.stopPropagation(), e.cancelBubble = !0, a.apply(this, arguments)) : void 0 : a.apply(this, arguments) }
this line e.currentTarget = e.currentTarget || this; throwed this error. why cann't it assign to read?
My package.json:
"devDependencies": { "extract-text-webpack-plugin": "^2.1.0", "html-webpack-plugin": "^2.28.0", "webpack": "^2.2.1", "webpack-livereload-plugin": "^0.10.0" }

[WeijianXu]

when I modified the code e.currentTarget = e.currentTarget || this; to this:
if (!e.currentTarget) { e.currentTarget = this; }. It worked well.

[johnsto]

FYI I'm encountering this error with similar code using Rollup.js w/Babel, so it's not Webpack-specific.