PHP error in Prevalent theme

Good day
My site is running fine, but I did a test to check for PHP errors and the following came up, which most likely is a theme error and not a plugin error:

Warning call_user_func_array() expects parameter 1 to be a valid callback, function ‘register_footer_menu’ not found or invalid function name / wp-includes/class-wp-hook.php:286

Line 286 in class-wp-hook.php looks like this: $value = call_user_func_array( $the_[‘function’], $args );

There is no mention of “register_footer_menu in this line and I am at a loss how to fix this.

Please advise and many thanks in advance.
Felix Heyl