Regression: Resource spawner in gz-sim fails after #376

[azeey]

Environment

• OS Version: Ubuntu 22.04
• Source or binary build? source, gz-fuel-tools9

Description

• Expected behavior: Resource Spawner in gz-sim works
• Actual behavior: Adding models from Resource Spawner in gz-sim does not work.

Steps to reproduce

1. Check out e125067 (gz-fuel-tools9_9.0.0) and build Gazebo from source. Start Gazebo and use the Resource Spawner. This should work.
2. Check out 934d28d and build Gazebo from source. Start Gazebo and use the Resource Spawner. This does not work.