Return null from loadTexture when image fails to load instead of wrongly creating a VideoTexture

[vincentfretin]

Description:

Previously, when an image failed to load (404), validateSrc in src-loader.js would fall back to treating the URL as a video, resulting in loadTexture returning a VideoTexture instead of indicating the error. (You got instead components:texture:warn './rainbow.jpg' is not a valid video). This made it difficult for callers to detect failed image loads.

Example in the community component media-image where I checked texture.image.tagName === "VIDEO" to know if the image was not found:
https://github.com/c-frame/aframe-gltf-model-plus/blob/6269b0499fcf497097d55375c4f10a70ae85d4c1/src/components/media-image.js#L68-L76

Changes proposed:

This change properly handles loading errors by:

• Updating checkIsImage to check for common image extensions before doing a HEAD request
• Updating loadTextureSource to reject the promise when resource is not found
• Updating loadTexture to call cb(null) when source loading fails
• Rejecting the promise in loadImageUrl when image request fails. Also fixed a typo in the error message format string ($s → %s).
• Using .then(cb, onRejected) instead of .then(cb).catch(onRejected) to avoid catching errors thrown by the callback itself

PR done with the help of Claude Code with Opus 4.5

[mrxz]

At this stage it's too early to conclude the resource would fail loading, as the status code might be in the 3XX range (redirects) or the server might not support HEAD requests (405). In those cases its still possible to load the image through the image tag.

[vincentfretin]

Good point. I made changes.

[vincentfretin]

The change was also wrong, assuming an error loading via the image tag meant not found. I reverted all that and instead check for common image extensions before doing a HEAD request. I had a similar patch in an aframe 1.6.0 project to not spam the server with HEAD requests because I used different images urls on a plane at regular interval like a slideshow.
Now the promise rejection happens on the ImageLoader error callback.