feat(account-tree-controller): add assert for account name prefix

[ccharly]

Explanation

Add a small assert to avoid having non-conventional group naming if our prefix is empty (those prefixes are not dynamic, so this should never happen anyway).

References

• fix(account-tree-controller): fix account name prefixes #6679 (comment)

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed, highlighting breaking changes as necessary
• I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes