Index: units/helpers/image_helper.php
===================================================================
--- units/helpers/image_helper.php	(revision 14733)
+++ units/helpers/image_helper.php	(working copy)
@@ -243,7 +243,7 @@
 			$transparent_index = imagecolortransparent($src_image_rs);
 
 			// if we have a specific transparent color
-			if ($transparent_index >= 0) {
+			if ( $transparent_index >= 0 && $transparent_index < imagecolorstotal($src_image_rs) ) {
 				// get the original image's transparent color's RGB values
 				$transparent_color = imagecolorsforindex($src_image_rs, $transparent_index);
 
@@ -260,7 +260,7 @@
 			}
 
 			// always make a transparent background color for PNGs that don't have one allocated already
-			if ($image_type == IMAGETYPE_PNG) {
+			if ( $image_type == IMAGETYPE_PNG ) {
 				// turn off transparency blending (temporarily)
 				imagealphablending($dst_image_rs, false);