[TIMOB-5887] Map annotation with external left button raises exception on clicking

A map annotation created with an external left button raises a FileNotFoundException on clicking. Although an exception occurs, I can see the left image getting displayed. This can be reproduced in KitchenSink->Views->Map View. In *Resources/examples/map_view.js*, at around line 33 we have:

var atlantaParams = {
                latitude:33.74511,
                longitude:-84.38993,
                title:"Atlanta, GA",
                subtitle:'Atlanta Braves Stadium\nfoo',
                animate:true,
                leftButton: '../images/atlanta.jpg',
                rightButton: Titanium.UI.iPhone.SystemButton.DISCLOSURE,
                myid:3 // CUSTOM ATTRIBUTE THAT IS PASSED INTO EVENT OBJECTS
};

*leftButton* is set to a local image here. Clicking on the Atlanta annotation works fine at this point. Now change *leftButton* to http://www.espncricinfo.com/favicon.png or http://facebook.com/favicon.ico or any other externally hosted PNG image. Now rebuild & click on the Atlanta annotation - you should see an exception being raised even though the left image was successfully displayed. This wasn't happening on 1.7.0 at least. The logcat output corresponding to the exception is attached.