#1081 Forum: gif can't be set as cover image

modules/boonex/forum/template/form_ghost_template.html

@@ -1,6 +1,6 @@
 <bx_include_base:../modules/base/text/template/form_ghost_template.html />
 <script>
 var aType = '{file_type}'.split('/');
-if(!aType || aType[0] != 'image' || !$.inArray(aType[1], ['gif', 'jpeg', 'png']))
+if(!aType || aType[0] != 'image' || -1 === $.inArray(aType[1], ['gif', 'jpeg', 'png']))
 	$('#bx-uploader-file-{storage_object}-{file_id} .bx-base-general-use-as-thumb').remove();
-</script>
+</script>