Fatal error

After the update of ultimte member to version 2.9.1, there is a fatal error whenever I want to view a user profile. Can you please help?

Thanks and regards

Fatal error:
Uncaught TypeError: gmdate(): Argument #2 ($timestamp) must be of type ?int, string given in /home/httpd/vhosts/hosting-root.ch/dcb_wp/wp-content/plugins/ultimate-member/includes/core/um-actions-profile.php:742 Stack trace: 0 /home/httpd/vhosts/hosting-root.ch/dcb_wp/wp-content/plugins/ultimate-member/includes/core/um-actions-profile.php(742): gmdate(‘Y-m-d H:i:s’, ‘2014-04-09 09:4…’) 1 /home/httpd/vhosts/hosting-root.ch/dcb_wp/wp-includes/class-wp-hook.php(324): um_profile_dynamic_meta_desc(”) 2 /home/httpd/vhosts/hosting-root.ch/dcb_wp/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters(NULL, Array) 3 /home/httpd/vhosts/hosting-root.ch/dcb_wp/wp-includes/plugin.php(517): WP_Hook->do_action(Array) 4 /home/httpd/vhosts/hosting-root.ch/dcb_wp/wp-includes/general-template.php(3064): do_action(‘wp_head’) 5 /home/httpd/vhosts/hosting-root.ch/dcb_wp/wp-content/themes/responsive/header.php(47): wp_head() 6 /home/httpd/vhosts/hosting-root.ch/dcb_wp/wp-includes/template.php(810): require_once(‘/home/httpd/vho…’) 7 /home/httpd/vhosts/hosting-root.ch/dcb_wp/wp-includes/template.php(745): load_template(‘/home/httpd/vho…’, true, Array) 8 /home/httpd/vhosts/hosting-root.ch/dcb_wp/wp-includes/general-template.php(48): locate_template(Array, true, true, Array) 9 /home/httpd/vhosts/hosting-root.ch/dcb_wp/wp-content/themes/responsive/page.php(20): get_header() 10 /home/httpd/vhosts/hosting-root.ch/dcb_wp/wp-includes/template-loader.php(106): include(‘/home/httpd/vho…’) 11 /home/httpd/vhosts/hosting-root.ch/dcb_wp/wp-blog-header.php(19): require_once(‘/home/httpd/vho…’) 12 /home/httpd/vhosts/hosting-root.ch/dcb_wp/index.php(17): require(‘/home/httpd/vho…’) 13 {main} thrown in /home/httpd/vhosts/hosting-root.ch/dcb_wp/wp-content/plugins/ultimate-member/includes/core/um-actions-profile.php on line 742