Error On Save / Update Post

I’ve found an error when I save a post. The incompatibility is with WordPress SEO (Yoast) 6.3.1
I got this error:

( ! ) Notice: Trying to get property of non-object in C:\Users\Torr\Sites\themehadoq.com\wp-content\plugins\easy-table-of-contents\easy-table-of-contents.php on line 594
Call Stack
# Time Memory Function Location
1 0.2010 441496 {main}( ) …\post.php:0
2 1.1091 40666912 edit_post( ) …\post.php:194
3 1.1301 40679864 wp_update_post( ) …\post.php:377
4 1.1481 40688624 wp_insert_post( ) …\post.php:3654
5 1.2511 40794496 do_action( ) …\post.php:3581
6 1.2511 40794768 WP_Hook->do_action( ) …\plugin.php:453
7 1.2511 40794768 WP_Hook->apply_filters( ) …\class-wp-hook.php:310
8 1.2821 40794192 WPSEO_Link_Watcher->save_post( ) …\class-wp-hook.php:288
9 1.2821 40794192 WPSEO_Link_Watcher->process( ) …\class-link-watcher.php:61
10 1.2821 40794192 apply_filters( ) …\class-link-watcher.php:114
11 1.2821 40794488 WP_Hook->apply_filters( ) …\plugin.php:203
12 1.2841 40801952 ezTOC::the_content( ) …\class-wp-hook.php:286
13 1.2841 40801952 ezTOC::build( ) …\easy-table-of-contents.php:1110
14 1.2841 40802000 ezTOC::extract_headings( ) …\easy-table-of-contents.php:924

( ! ) Notice: Trying to get property of non-object in C:\Users\Torr\Sites\themehadoq.com\wp-content\plugins\easy-table-of-contents\easy-table-of-contents.php on line 595
Call Stack
# Time Memory Function Location
1 0.2010 441496 {main}( ) …\post.php:0
2 1.1091 40666912 edit_post( ) …\post.php:194
3 1.1301 40679864 wp_update_post( ) …\post.php:377
4 1.1481 40688624 wp_insert_post( ) …\post.php:3654
5 1.2511 40794496 do_action( ) …\post.php:3581
6 1.2511 40794768 WP_Hook->do_action( ) …\plugin.php:453
7 1.2511 40794768 WP_Hook->apply_filters( ) …\class-wp-hook.php:310
8 1.2821 40794192 WPSEO_Link_Watcher->save_post( ) …\class-wp-hook.php:288
9 1.2821 40794192 WPSEO_Link_Watcher->process( ) …\class-link-watcher.php:61
10 1.2821 40794192 apply_filters( ) …\class-link-watcher.php:114
11 1.2821 40794488 WP_Hook->apply_filters( ) …\plugin.php:203
12 1.2841 40801952 ezTOC::the_content( ) …\class-wp-hook.php:286
13 1.2841 40801952 ezTOC::build( ) …\easy-table-of-contents.php:1110
14 1.2841 40802000 ezTOC::extract_headings( ) …\easy-table-of-contents.php:924

( ! ) Notice: Trying to get property of non-object in C:\Users\Torr\Sites\themehadoq.com\wp-content\plugins\easy-table-of-contents\easy-table-of-contents.php on line 596
Call Stack
# Time Memory Function Location
1 0.2010 441496 {main}( ) …\post.php:0
2 1.1091 40666912 edit_post( ) …\post.php:194
3 1.1301 40679864 wp_update_post( ) …\post.php:377
4 1.1481 40688624 wp_insert_post( ) …\post.php:3654
5 1.2511 40794496 do_action( ) …\post.php:3581
6 1.2511 40794768 WP_Hook->do_action( ) …\plugin.php:453
7 1.2511 40794768 WP_Hook->apply_filters( ) …\class-wp-hook.php:310
8 1.2821 40794192 WPSEO_Link_Watcher->save_post( ) …\class-wp-hook.php:288
9 1.2821 40794192 WPSEO_Link_Watcher->process( ) …\class-link-watcher.php:61
10 1.2821 40794192 apply_filters( ) …\class-link-watcher.php:114
11 1.2821 40794488 WP_Hook->apply_filters( ) …\plugin.php:203
12 1.2841 40801952 ezTOC::the_content( ) …\class-wp-hook.php:286
13 1.2841 40801952 ezTOC::build( ) …\easy-table-of-contents.php:1110
14 1.2841 40802000 ezTOC::extract_headings( ) …\easy-table-of-contents.php:924

( ! ) Warning: Cannot modify header information – headers already sent by (output started at C:\Users\Torr\Sites\themehadoq.com\wp-content\plugins\easy-table-of-contents\easy-table-of-contents.php:594) in C:\Users\Torr\Sites\themehadoq.com\wp-admin\post.php on line 198
Call Stack
# Time Memory Function Location
1 0.2010 441496 {main}( ) …\post.php:0
2 1.5711 40812144 setcookie ( ) …\post.php:198

( ! ) Warning: Cannot modify header information – headers already sent by (output started at C:\Users\Torr\Sites\themehadoq.com\wp-content\plugins\easy-table-of-contents\easy-table-of-contents.php:594) in C:\Users\Torr\Sites\themehadoq.com\wp-includes\pluggable.php on line 1216
Call Stack
# Time Memory Function Location
1 0.2010 441496 {main}( ) …\post.php:0
2 1.5901 40812112 redirect_post( ) …\post.php:201
3 1.5911 40812184 wp_redirect( ) …\post.php:1870
4 1.5911 40812296 header ( ) …\pluggable.php:1216