Function useOptionalBoundSyncExternalStore

useOptionalBoundSyncExternalStore<
    S extends { subscribe(onStoreChange: () => void): () => void },
    T,
>(
    store: S | null | undefined,
    getSnapshot: (store: S) => T,
): T | null
Like useBoundSyncExternalStore, but for a store that may be absent (null/undefined) — the bound-method analog of useOptionalSyncExternalStore. It calls store.subscribe(...) and the snapshot selector on the instance, so a normal this-centric class whose methods are NOT pre-bound works without the caller detaching them (which would strip this); returns the snapshot, or null when there is no store.
Type Parameters
- S extends { subscribe(onStoreChange: () => void): () => void }
  The store type; must expose a subscribe(listener) method.
- T
  The snapshot value type.
Parameters
- store: S | null | undefined
- getSnapshot: (store: S) => T
Returns T | null

Remarks
Pass the store instance (or null/undefined) and a selector that reads the snapshot off it (s => s.getState()). subscribe is memoized on the store identity so it stays a stable reference across renders; the snapshot selector may be an inline arrow. The null snapshot doubles as the SSR snapshot, keeping it SSR-safe.