Remove invalid build (or tag) from persisted meta data on error

[freezy]

Use case:

1. Author starts uploading a new release (or version), adds a tag or build
2. Build gets deleted
3. When submitting, though the tag or build isn't in the DB nor selectable anymore, it's still on local storage and will be submitted

Fix: Either check against valid IDs when rendering the page or clear local storage on error (first preferred).