4.1.0 Breaks popper.js in IE11: #26325

4.1.0 breaks tooltips and popovers in IE11:

https://jsbin.com/siqewopovu/edit?html,js,output

In my browser, the tooltips in that JSBin simply degrade to classic tooltips.

When debugging my project in VS 2017 (where I am actually using bootstrap.bundle.min.js), I stop on this error:

Unhandled exception in bootstrap.bundle.min.js:
JavaScript runtime error: Object.keys argument is not an Object

The root exception seems to occur deep in the call stack, in rollupPluginBabelHelpers, in the line var ownKeys = Object.keys(source); below:

function _objectSpread(target) {
  for (var i = 1; i < arguments.length; i++) {
    var source = arguments[i] != null ? arguments[i] : {};
    var ownKeys = Object.keys(source);

    if (typeof Object.getOwnPropertySymbols === 'function') {
      ownKeys = ownKeys.concat(Object.getOwnPropertySymbols(source).filter(function (sym) {
        return Object.getOwnPropertyDescriptor(source, sym).enumerable;
      }));
    }

    ownKeys.forEach(function (key) {
      _defineProperty(target, key, source[key]);
    });
  }

  return target;
}

Simply reverting the script reference to BS v4.0.0 prevents the problem.