AssimpLoader: Embedded texture are not handles correctly

[kimkulling]

Describe the bug
When a material is using an embedded texture coming from assimp it will ignored.

To Reproduce

1. Open issue with embedded textures
   a. https://nasa3d.arc.nasa.gov/detail/acrimsat
2. Check for loaded embedded textures
   Expected behavior
   Embedded textures shall be loaded.

Screenshots
NA

Desktop (please complete the following information):

• OS: All

Additional context
Add any other context about the problem here.