BO - customer service / forward message mail is incomplete if the message is intended for a non-employee

[SD1982]

Describe the bug

In the customer service section if you forward a message to an email address that does not belong to an employee of the shop the email is then incomplete

Expected behavior

The mail content should be the same for all the forward option

Steps to Reproduce

Steps to reproduce the behavior:

Before test => setup the smtp parameters

1. Go to BO and create a new employee
2. Go to FO and create an order
3. In the order confirmation page send a message to customer service
4. Go to BO in the customer service page and go to the previously send message detail
5. Forward the message to the previously created employee =>result : OK => - the mail look like this:
   
6. Now try to forward the message to a non-employee with this option :
   
7. See error => the mail is incomplete and look like this:
   

Additional information

• PrestaShop version: 1.7.7.x /// 1.7.8.x /// develop
• PHP version: reproduced on 7.2 and 7.3