Attempt to fix errors issues with Discord sign-in (fixes #312)

[vcarl]

This should be it? They’re both in places that are checking existence so this should be fine

[what-the-diff]

PR Summary

• Enhancement in User Property Handling in DiscordAuth.tsx
  The user property within the DiscordAuth.tsx file now has an "optional chaining" feature. This ensures the application can better anticipate and handle situations where certain properties might be undefined.

• Improved Safety Measures in discordcb.tsx
  Similar improvements have also been made in the discordcb.tsx file. The user property here too, now supports optional chaining. This helps in maintaining consistent functionality across different parts of the application.

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