Upload button greyed out in IE, but works in Firefox

I've been having a problem with the upload button being greyed out in IE, but not in Firefox. It seemed different from the greyed-out upload buttons in other issues, as the Upload module's already activated and permissions're already set. Plus, it works just fine in one browser, yet not at all in another.

In IE, I got an error (by clicking on the little exclamation mark to get the page errors) saying something was wrong on line 107 of libraries/swfupload/swfupload.js

Turns out there's a variable there called path, which is never initialized. Changing this:

	if (indexSlash <= 0) {
		path = "/";
	} else {
		path = window.location.pathname.substr(0, indexSlash) + "/";
	}

to

	if (indexSlash <= 0) {
		var path = "/";
	} else {
		var path = window.location.pathname.substr(0, indexSlash) + "/";
	}

fixes the problem.