A confusing error message is shown if devvit.yaml is accidentally emptied and `devvit upload` is run

[fsvreddit]

If the devvit.yaml file has accidentally been emptied, devvit upload doesn't handle this elegantly with a useful user-facing error message.

PS C:\code\reddithelp-bot> devvit upload
Checking for updates...... ✅
    TypeError: Cannot read properties of undefined (reading 'packageManager')

It would be useful if the error message was more descriptive.