Function guarded

guarded(step: string, handler: () => void): () => void
Runs handler as a request's success handler: an exception out of it would abort the transaction too.
Parameters
- step: string
  The migration step, as the log names it.
- handler: () => void
  The success handler to run.
Returns () => void
The handler to assign to onsuccess — it never throws.
Example
```
request.onsuccess = guarded("v7 repair", () => {
    store.put(request.result);
});
```
- Defined in packages/core/src/capabilities/offline/db/upgrade-guards.ts:49