I followed the instructions here: https://support.zendesk.com/hc/en-us/articles/203660056-Salesforce-Creating-custom-links-in-Salesforce-Zendesk-Ticket#creating-a-trigger

This trigger works except that row 7 assumes that at least 1 record is found. If not it throws an error 'List has no rows for assignment to SObject' if there is not a record available for assignment. 

I found this answer: https://help.salesforce.com/articleView?id=000159853&type=1

And have tried to incorporate it but I keep getting errors. Can anyone give some guidance on how to rewrite this? 

I followed the instructions here: https://support.zendesk.com/hc/en-us/articles/203660056-Salesforce-Creating-custom-links-in-Salesforce-Zendesk-Ticket#creating-a-trigger

This trigger works except that row 7 assumes that at least 1 record is found. If not it throws an error 'List has no rows for assignment to SObject' if there is not a record available for assignment. 

I found this answer: https://help.salesforce.com/articleView?id=000159853&type=1

And have tried to incorporate it but I keep getting errors. Can anyone give some guidance on how to rewrite this?