BO - An exception is generated while clicking to preview the dropdown-menu of Email Theme with multistore when no order created

[HanaRebaiQA]

Prerequisites

• I understand and accept the project's code of conduct
• I have already searched in existing issues and found no previous report of this bug.

Describe the bug and add screenshots

While clicking to preview the dropdown-menu of Email Theme with a new shop created (not the default one) when no order is created ==> Exception

See screen-record below :
https://watch.screencastify.com/v/uH19Lz9O8tNh17XVyCOq

Expected behavior

The content of all the dropdown-menu of Email Theme when choose the new shop created are well displayed. No exception is generated.

Steps to reproduce

1. Enable multistore and create a new shop
2. Verify that there is no order created
3. BO>IMPROVE>Design>Email Theme
4. Change the shop of the new one created
5. Click on the loop of classic / modern
6. Click on Http ==> See Error > Exception is generated
7. Click on the ropdown-menu and Preview ==> See Error > Exception is generated

PrestaShop version(s) where the bug happened

1.7.7.8 & 1.7.8.1 & 1.7.8.x

PHP version(s) where the bug happened

7.3

If your bug is related to a module, specify its name and its version

No response