File Upload Error + Bad Words Filter

Description:

Before upgrading to 3.17.0, the file upload feature was working flawlessly. Users were able to drag and drop pictures and other types of files. As soon as I deployed the 3.17.0 update, our users started complaining about an error they get when they were trying to upload a file.

Steps to reproduce:

1. Open any message window (Group or private)
2. Upload any type of document (We use a lot of screenshots for sharing issues)
3. An error "Cannot read property of "0" null" will occur

Expected behavior:

In the previous version, it was working as expected.

Actual behavior:

In the new version, it would give the user an error for any type of file upload.

Server Setup Information:

• Version of Rocket.Chat Server: 3.17.0
• Operating System: Ubuntu 20
• Deployment Method: Docker Image
• Number of Running Instances: 1
• DB Replicaset Oplog: *
• NodeJS Version: 12.22.1
• MongoDB Version: 4.0.26

Client Setup Information

• Desktop App or Browser Version: Desktop App 3.2.3 | Firefox
• Operating System: Windows 10 | Ubuntu

Additional context

By checking the log, I was able to pinpoint the issue to make it work. It seems that issue is tied to the bad words filtering feature as shown in the log below. In a corporate environment, the bad words filtration is a must.

Relevant logs:

This was from my staging server.

Reproduce the failure on Rocket.Chat 3.17.0 using the reported file-upload steps with bad-words filtering enabled. Start by inspecting the server log around the filtering error and the file-upload entry point. Done means uploads succeed for documents and images while the bad-words filter remains enabled.