Error in regular post preview (using BeTheme)

Hi there,
When doing a regular preview of a draft post, using certain modules from the visual builder in BeTheme (Muffin Builder), I get this error:

Warning: Creating default object from empty value in /home/couragem/public_html/wp-content/plugins/simple-preview/simple-preview.php on line 140

Fatal error: Uncaught Error: Call to a member function get_gallery_attachment_ids() on null in /home/couragem/public_html/wp-content/themes/betheme/functions/theme-shortcodes.php:1530 Stack trace: #0 /home/couragem/public_html/wp-content/themes/betheme/functions/builder/front.php(1051): sc_shop_slider(Array) #1 /home/couragem/public_html/wp-content/themes/betheme/functions/builder/front.php(408): mfn_print_shop_slider(Array) #2 /home/couragem/public_html/wp-content/themes/betheme/includes/content-single.php(225): mfn_builder_print(7804) #3 /home/couragem/public_html/wp-includes/template.php(690): require('/home/couragem/...') #4 /home/couragem/public_html/wp-includes/template.php(647): load_template('/home/couragem/...', false) #5 /home/couragem/public_html/wp-includes/general-template.php(155): locate_template(Array, true, false) #6 /home/couragem/public_html/wp-content/themes/betheme/single.php(60): get_template_part('includes/conten...', 'single') #7 /home/couragem/public_html/wp-includes/template-loader.php(74): inclu in /home/couragem/public_html/wp-content/themes/betheme/functions/theme-shortcodes.php on line 1530

Any suggestions?