Hi,
There are not a lot of issues. What you have in your attachment is the extended debug information for ONE error.
Unfortunately, you didn't provide the first line(s) of the error message, and thus we're missing the file path where the problem happens. Basically, as a comparison, it's like if you gave me the google maps itinerary to your street, but not the street number, so I don't which house you're in, but I know you're not far.
However, based on what is written in it, it seems that you reproduced the issue by clicking on the "email" button of an order;
In that case, it is the "order notification" email which is loaded, not the "order admin notification" email.
So the problem is likely with the file media/com_hikashop/mail/order_notification.preload.modified.php
rename it via FTP and try again and it should work.
Reinstalling HikaShop won't help. The problem is not in HikaShop. It's in a customization you've made in the past.