Normal Map node with 'buffer' disabled prevents images loading when opening ptex

[Airyzz]

Material Maker version:

1b32348

OS/device including version:

Pop!_OS 22.04 LTS

Issue description:

When loading a ptex file, some image files are not loaded correctly. The images will still show on the ImageButton on the node, and in preview3d but they will not render in the preview2d, nor in export animation.

Steps to reproduce: Create a setup like the following:

If you save to disk, and reload the ptex file, when clicking on the image node, the preview2d is not loading correctly:

Note that the normal map node MUST be plugged in to the material output. if it is not plugged in, then the preview2d will load just fine

I have attached reproduction project files here: reproduction.zip

[Airyzz]

having worked with it a bit more, this doesnt necessarily seem specific to normal map, i'm seeing similar issues sometimes if there is just a texture plugged in to the output material, as well as sometimes just trying to export an animation which depends on any image. This normal map method seems to be the most reliable way to reproduce the issue though