Suggested change to map marker load failures.

[GoogleCodeExporter]

I changed these two "die()" to "echo+return" instead, it provides a gracious 
failure that I can then respond to in other code.

die('GoogleMapAPI:createMarkerIcon: Error reading image: ' . $iconImage);
TO
echo ('GoogleMapAPI:createMarkerIcon: Error reading image: ' . $iconImage);   
return;

AND

die('GoogleMapAPI:createMarkerIcon: Error reading shadow image: ' . 
$iconShadowImage);

TO

echo ('GoogleMapAPI:createMarkerIcon: Error reading shadow image: ' . 
$iconShadowImage);
return; 

Original issue reported on code.google.com by anderson...@gmail.com on 12 Aug 2014 at 6:33