Default url aliases not applying on content items

Problem/Motivation

In the 2.x alpha version of the module existing content items which had url aliases from core no longer have those aliases working / being applied to them

Steps to reproduce

1. Initially set up the site with domain version 2.x and domain path version 1.5.x (do not enable domain_path yet)
2. Create multiple content items and ensure that they have url aliases added to them
3. Enable domain path module and observe that existing aliases still work and show as expected and the user is able to create and add domain specific url aliases
4. Update domain module to 3.x and update domain_path to 2.x (alpha2)
5. Now observe that existing content items which had url aliases from core no longer have these aliases working, instead just the default node path of /node/{id} is showing

Proposed resolution

Add back in code snippet that was lost in #3563256 which ensure that the path would fall back to the core's url alias.

Remaining tasks

Create MR with bugfix