fix for Exif errors on non-Exif JPEGs

[krorick]

RE version 1.7.9-20090308

I'd like to propose a change to the module.graphic.jpg.php library file.

The current version will attempt to parse non-exif images and generates a confusing (to the end user anyway) error.

My solution is to add a check on line 57:

current: if (function_exists('exif_read_data')) {
fix: if (function_exists('exif_read_data') && strpos ($imageinfo['APP1'], 'Exif') === 0) {