Fatal Error when Customizing

Hi! I’m getting this error when entering the customize my wordpress frontend.

Steps to error:
1- Enter wp-admin
2- Go to Appearence/Edit CSS

Thank you for your help!

Fatal Error
Line 105
Message Uncaught Error: Call to a member function get() on null in /home/huertinu/public_html/wp-content/plugins/woo-free-shipping-bar/wfspb-front-end.php:105 Stack trace: #0 /home/huertinu/public_html/wp-includes/class-wp-hook.php(286): WFSPB_F_FrontEnd->enqueue_script_fontend(”) #1 /home/huertinu/public_html/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters(NULL, Array) #2 /home/huertinu/public_html/wp-includes/plugin.php(465): WP_Hook->do_action(Array) #3 /home/huertinu/public_html/wp-includes/script-loader.php(2537): do_action(‘wp_enqueue_scri…’) #4 /home/huertinu/public_html/wp-includes/class-wp-customize-manager.php(455): wp_enqueue_scripts() #5 /home/huertinu/public_html/wp-includes/class-wp-customize-manager.php(552): WP_Customize_Manager->wp_die(0, ‘Non-existent ch…’) #6 /home/huertinu/public_html/wp-includes/class-wp-hook.php(286): WP_Customize_Manager->setup_theme(”) #7 /home/huertinu/public_html/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters(”, Array) #8 /home/huertinu/public_h
File /home/huertinu/public_html/wp-content/plugins/woo-free-shipping-bar/wfspb-front-end.php

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