fix(ramps): adds error message if user tries to sell zero balance token

[georgeweiler]

Description

An error message is now displayed if the user tries to sell a token when they have zero balance.

Fixes https://github.com/MetaMask/metamask-mobile/issues/16404

Related issues

Fixes:

Manual testing steps

1. Go to this page...

Screenshots/Recordings

Before

After

Pre-merge author checklist

• [ ] I’ve followed MetaMask Contributor Docs and MetaMask Mobile Coding Standards.
• [ ] I've completed the PR template to the best of my ability
• [ ] I’ve included tests if applicable
• [ ] I’ve documented my code using JSDoc format if applicable
• [ ] I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• [ ] I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• [ ] I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.