Eloquent Resource whenPivotLoaded doesn't work when using custom accessor

[GeorgThomassen]

• Laravel Version: 5.7.2
• PHP Version: 7.2.9
• Database Driver & Version: MariaDB 10.3.9

Description:

When using the ->whenPivotLoaded method on a Resource where the underlying Eloquent model has aliased the pivot accessor with ->as('accessor') no value is returned. ConditionallyLoadsAttributes.php only tries to access the pivot table using ->pivot which is null after changing the accessor.

Steps To Reproduce:

Create two models in a many-to-many relationship.
Eager load the relationship.
Change the accessor of the pivot table with the ->as() method.
Create a Resource and return a value based on whenPivotLoaded