fixes #2507 add conditions before trying to display an image in the email

themes/default/template/mail/text/html/cat_group_info.tpl

@@ -1,6 +1,8 @@
 <div id="cat_group_info">
 <h2>{'Informations'|@translate}</h2>
+{if isset($IMG) && isset($IMG.link) && isset($IMG.src)}
 <p><a href="{$IMG.link}" class="thumblnk"><img src="{$IMG.src}"></a></p>
+{/if}
 <p>{'Hello,'|@translate}</p>
 <p>{'Discover album:'|@translate} <a href="{$LINK}">{$CAT_NAME}</a></p>
 <p>{$CPL_CONTENT}</p>