Index: wp-includes/media.php
===================================================================
--- wp-includes/media.php	(revision 7135)
+++ wp-includes/media.php	(working copy)
@@ -73,6 +73,8 @@
 			$width = $info[0];
 			$height = $info[1];
 		}
+		else
+			return false;
 	}
 	elseif ( isset($meta['width'], $meta['height']) ) {
 		// any other type: use the real image and constrain it