Editor: Make sure to log an unsupported extension

[gero3]

I wanted to load an exr file in the editor. So I tried to import the file in the editor. Nothing seemed to happen. Checking the dev tools didn't help either. The exr file isn't supported in the editor, I found that out by debugging the editor.

To Reproduce:

• Import an exr file in the editor

Issue

• Nothing happens

Solution

• Log if the extension is not supported and make sure not to block because of multiple files loading.

[Mugen87]

make sure not to block because of multiple files loading.

That's the reason why not using alert(), right? I still think that using alert() is better in this context since a lot of users (beginners, non-developers) don't check the browser console.

[gero3]

That's the reason why not using alert(), right? I still think that using alert() is better in this context since a lot of users (beginners, non-developers) don't check the browser console.

I didn't use alerts because @mrdoob commented that line specifically when adding multiple file support. But I'm willing to change it to an alert because it is worse without warning the users.

@Mugen87 I'll update it if you still think so.

[Mugen87]

Um, I see. In this case I vote to only change the default branch in this PR and don't change the existing usage of alert().

[mrdoob]

Thanks!