Error on website

I am getting errors on many of the pages of my website. Kindy help me resolve the issue.

( ! ) Notice: Undefined index: bbp_template_after_before_topic in /var/www/html/wp-content/plugins/header-footer/plugin.php on line 260
Call Stack
# Time Memory Function Location
1 0.0001 383840 {main}( ) …/index.php:0
2 0.0001 384576 require( ‘/var/www/html/wp-blog-header.php’ ) …/index.php:17
3 0.1854 16680416 require_once( ‘/var/www/html/wp-includes/template-loader.php’ ) …/wp-blog-header.php:19
4 0.1914 16895632 apply_filters( ) …/template-loader.php:73
5 0.1914 16896032 WP_Hook->apply_filters( ) …/plugin.php:203
6 0.1914 16897536 bbp_template_include( ) …/class-wp-hook.php:298
7 0.1914 16897536 apply_filters( ) …/sub-actions.php:436
8 0.1914 16897936 WP_Hook->apply_filters( ) …/plugin.php:203
9 0.1918 16900680 bbp_template_include_theme_compat( ) …/class-wp-hook.php:298
10 0.1919 16901056 BBP_Shortcodes->display_topic( ) …/theme-compat.php:622
11 0.1928 16973512 bbp_get_template_part( ) …/shortcodes.php:355
12 0.1928 16974040 bbp_locate_template( ) …/template-functions.php:43
13 0.1929 16975072 load_template( ) …/template-functions.php:105
14 0.1930 16982496 require( ‘/var/www/html/wp-content/plugins/bbpress/templates/default/bbpress/content-single-topic.php’ ) …/template.php:690
15 0.1957 17063200 do_action( ) …/content-single-topic.php:16
16 0.1957 17063576 WP_Hook->do_action( ) …/plugin.php:453
17 0.1957 17063576 WP_Hook->apply_filters( ) …/class-wp-hook.php:323
18 0.1957 17064704 hefo_bbp_template_before_single_topic( ) …/class-wp-hook.php:298