Uploaded animated WEBP files do not post for download

Description:

When uploading an animated WEBP file, it appears to upload successfully, but doesn't become available in the channel it was uploaded to. No post occurs following the upload. Still WEBP images work properly; only animated variants are broken.

Server Setup Information:

• Version of Rocket.Chat Server: 0.63.3
• Operating System: Mac OS 10.13.4/Windows 10
• Deployment Method(snap/docker/tar/etc): All
• Number of Running Instances: 1
• DB Replicaset Oplog:
• Node Version:
• mongoDB Version:

Steps to Reproduce:

1. Attempt to upload an animated WEBP file. As these are uncommon still, here's an example.
2. Watch it upload as any standard file.
3. View results.

Expected behavior:

The file should be visible in the channel to download. In the apps, and in supported browsers (Chrome and Opera currently, as this is a proprietary Google format), the image should render.

Actual behavior:

No post appears and the file is not available in the channel view.

Relevant logs:

Start by reproducing the upload in the channel view with the linked animated WEBP example and compare it with a still WEBP upload. The issue names no source file, test, or entry point; done means the animated file creates a channel post, is downloadable, and renders where supported.