Events sometimes emitted with undefined file

[mifi]

This has caused many errors like «cannot read properies of undefined» in the wild. I think we should prevent events from being emitted after a file has been set to undefined.
See #3811

Event that sometimes get emitted with file argument undefined:

• upload-error
• upload-started
• upload-progress
• upload-success
• preprocess-progress
• preprocess-complete
• postprocess-progress
• postprocess-complete
• dashboard:file-edit-complete
• file-added
• file-removed

So we need to search for all occurrences of each of these, and make sure that we don't emit an undefined file argument.

For example here:

uppy/packages/@uppy/transloadit/src/index.js

Line 619 in 3121fae

this.uppy.emit('upload-error', file, err)

we should probably return before emitting any events, or maybe better make sure files are only ever deleted after an upload has finished or failed.

[Murderlon]

Can we make this issue more specific? It's not really actionable at the moment.

[mifi]

I updated the description

[heloineto]

When does this happen?

Is it when the user deletes the file before it's finished uploading?

[Murderlon]

We haven't seen this happen anymore so the issue is not reproducible. Luckily we are migrating everything to TS, then we can make sure things are happening correctly.