TypeError on array_merge() in LearningPathContentController

Problem/Motivation

When scaffolding out a training in the Learning Path Manager, opening the Activities section results in a partially empty screen. The following error appears in the log:

TypeError: array_merge(): Argument #2 must be of type array, int given in array_merge() (line 390 of /var/www/html/web/modules/contrib/opigno_learning_path/src/Controller/LearningPathContentController.php).

The $items variable seems to contain a module, not a course:

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes