Fatal error when viewing blog comments

Hi

When we click to view the pending blog comments we're getting this error...

Fatal error: Uncaught Error: Call to a member function form_start() on null in /home/facemed/HI55G2I2/htdocs/cms/addons/apps/perch_blog/modes/comment.edit.post.php:7 Stack trace: #0 /home/facemed/HI55G2I2/htdocs/cms/addons/apps/perch_blog/comments/edit/index.php(26): include() #1 {main} thrown in /home/facemed/HI55G2I2/htdocs/cms/addons/apps/perch_blog/modes/comment.edit.post.php on line 7

ars($matches) { $url_vars = $this->tmp_url_vars; if (isset($url_vars[$matches[1]])){ return $url_vars[$matches[1]]; } } private function _load_author() { $Cache = PerchBlog_Cache::fetch(); $cached_authors = $Cache->get('authors'); if (!$cached_authors) { $Authors = new PerchBlog_Authors; $authors = $Authors->all(); if (PerchUtil::count($authors)) { $cached_authors = array(); foreach($authors as $Author) { $cached_authors[$Author->id()] = $Author; } $Cache->set('authors', $cached_authors); } } if ($cached_authors) { if (isset($cached_authors[$this->authorID()])) { $this->Author = $cached_authors[$this->authorID()]; return true; } } return false; } private function _load_section() { $Cache = PerchBlog_Cache::fetch(); $cached_sections = $Cache->get('sections'); if (!$cached_sections) { $Sections = new PerchBlog_Sections; $sections = $Sections->all(); if (PerchUtil::count($sections)) { $cached_sections = array(); foreach($sections as $Section) { $cached_sections[$Section->id()] = $Section; } $Cache->set('sections', $cached_sections); } } if ($cached_sections) { if (isset($cached_sections[$this->sectionID()])) { $this->Section = $cached_sections[$this->sectionID()]; return true; } } return false; } private function _load_blog() { $Cache = PerchBlog_Cache::fetch(); $cached_blogs = $Cache->get('blogs'); if (!$cached_blogs) { $Blogs = new PerchBlog_Blogs; $blogs = $Blogs->all(); if (PerchUtil::count($blogs)) { $cached_blogs = array(); foreach($blogs as $Blog) { $cached_blogs[$Blog->id()] = $Blog; } $Cache->set('blogs', $cached_blogs); } } if ($cached_blogs) { if (isset($cached_blogs[$this->blogID()])) { $this->Blog = $cached_blogs[$this->blogID()]; return true; } } return false; } private function array_prefix_match($prefix, $array) { if (!is_array($array)) return false; foreach ($array as $v) { if (strpos($v, $prefix)===0) return true; } return false; } }

Diagnostics (there is no debug message)...

Perch: 3.0.10, PHP: 7.0.22, MySQL: mysqlnd 5.0.12-dev - 20150407 - $Id: b5c5906d452ec590732a93b051f3827e02749b83 $, with PDO
Server OS: Linux, cgi-fcgi
Installed apps: content (3.0.10), assets (3.0.10), categories (3.0.10), perch_blog (5.6.1), perch_events (1.9.5), perch_forms (1.9), perch_members (1.6.1)
App runtimes: <?php $apps_list = [ 'perch_forms', 'perch_events', 'perch_members', 'perch_blog' ];
PERCH_LOGINPATH: /cms
PERCH_PATH: /home/facemed/HI55G2I2/htdocs/cms
PERCH_CORE: /home/facemed/HI55G2I2/htdocs/cms/core
PERCH_RESFILEPATH: /home/facemed/HI55G2I2/htdocs/cms/resources
Image manipulation: GD Imagick
PHP limits: Max upload 128M, Max POST 128M, Memory: 256M, Total max file upload: 128M
F1: 3b606135b33e6a102526838f4152a807
Resource folder writeable: Yes
HTTP_HOST: facemed.co.uk
DOCUMENT_ROOT: /home/facemed/HI55G2I2/htdocs/
REQUEST_URI: /cms/core/settings/diagnostics/
SCRIPT_NAME: /cms/core/settings/diagnostics/index.php