[TIMOB-8008] MobileWeb : Utils - Ti.Utils.base64encode() is causing an error of "INVALID_CHARACTER_ERR: DOM Exception"

Steps to reproduce: 1. Create a default mobile web app and replace the code in app.js with the following

var win = Titanium.UI.createWindow({
			title : 'test',
			backgroundColor : 'white'
		});

win.open();

var f = Ti.Filesystem.getFile(Ti.Filesystem.resourcesDirectory, 'KS_nav_ui.png');
		var blob = f.read();
		var encoded = Ti.Utils.base64encode(blob);

		alert(encoded);

Actual result: An error of "INVALID_CHARACTER_ERR: DOM Exception" is caused by the line var encoded = Ti.Utils.base64encode(blob); Expected result: An alert is displayed with a base 64 version of the file