Fix: Don't call Object.keys on non-objects (babel#10482)

[chrishinrichs]

Q	A
Fixed Issues?	Fixes #10482
Patch: Bug Fix?	Yes
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

This changes the polyfill for the object spread operator to ensure that the argument to be spread is an Object before calling Object.keys. This fixes a JS error in IE11 which implements the old ES5 version of Object.keys which does not support non-object arguments.

A common pattern that will run into this issue:

const someBool = false;
const obj = {
  ...someBool && { foo: 'bar' }
};

[ljharb]

it would be better to do this:

Suggested change

	var ownKeys = Object.keys(source);
	var ownKeys = Object.keys(Object(source));

[chrishinrichs]

Thanks for the review! I have made the suggested change @ljharb, can you take another look?

[nicolo-ribaudo]

My initial reaction about the issue was "you just need to load a polyfill", but given that the fix is so simple I don't see why we shouldn't include it.