Undefined Index & Undefined Offset 0 Error

Hello,

I implemented this SEO title tag plugin on this site https://www.trinityexteriorsinc.com/ when I make changes in contact us page following errors appear,

Notice: undefined index: title tag in /home/trinityexteriorsinc.com/wp-content/plugins/seo-title-tag/seo-title-tag-3.4-php on line 801

Notice: undefined offser: 0 in /home/trinityexteriorsinc.com/wp-content/plugins/seo-title-tag/seo-title-tag-3.4-php on line 803

These errors repeat three times then following warning appears

Warning: cannot modify header information- headers already sent by (output started at home/trinityexteriorsinc.com/wp-content/plugins/seo-title-tag/seo-title-tag-3.4-php on line 801) in home/trinityexteriorsinc.com/wp-admin/post.php on line 233

Warning: cannot modify header information- headers already sent by (output started at home/trinityexteriorsinc.com/wp-content/plugins/seo-title-tag/seo-title-tag-3.4-php on line 801) in home/trinityexteriorsinc.com/wp-includes/pluggable.php on line 896

Please help me fixing this issue asap.

Thanks.
https://www.ads-software.com/plugins/seo-title-tag/

https://www.ads-software.com/plugins/seo-title-tag/