Traverse.has always return true if the node is undefined

[jfmmm]

A bit of an edge case, but we were passing an object to traverse that could possibly be undefined, then using has to check if the object contained or not a path. Then if it returns false we would do something else.

It worked fine in 0.6.8, but since we updated has always returned true in those cases, which obviously seems wrong.

I tracked it to here where node && was added in the for loop, causing it to always return true when the node is undefined.

/** @type {(ps: PropertyKey[]) => boolean} */
Traverse.prototype.has = function (ps) {
	var node = this.value;
	for (var i = 0; node && i < ps.length; i++) {
		var key = ps[i];
		if (!hasOwnProperty.call(node, key) || (!this.options.includeSymbols && typeof key === 'symbol')) {
			return false;
		}
		node = node[key];
	}
	return true;
};

Here an example

import traverse from "traverse";

const tr = traverse(undefined);
const hasPath = tr.has(['my', 'path']);

console.log(hasPath); // return true

I'm gonna fix it on our side since there's no point in even calling traverse in those cases, but felt I should report it anyway.

[ljharb]

require('.')(undefined).has([]) seems to return true for me in every traverse version, including v0.6.8 - however, require('.')(undefined).has(['my', 'path']) indeed returns false until v0.6.9.

Looks like this broke in #6. I'll fix it ASAP.