Lead Developer
Hi Petr,
Haven’t experienced this before.
The warning has to do with this piece of code: $wp_customize->get_section('static_front_page')
As we can see in the WP codex, static_front_page is a value we can use: https://codex.wordpress.org/Class_Reference/WP_Customize_Manager/add_section
What version of WordPress are you running?
Let me know – we’ll get it fixed! 🙂