bug: Users can press the send button while an attachment is being uploaded

### What happened?

## Reproduction steps
1. Attach any image to a message
2. Press the send button while it's uploading
3. Wait until the message(s) send

## App information
App ID: chat.revolt
App Version: 1.3.6b
App Type: GPAA
API Host: api.revolt.chat
API Version: 0.8.8
Runtime SDK: 36
Model: Google Lynx (Pixel 7a)