fix: add unknown option to current state (#887)

Author: ashton-huxtable

packages/core/src/flushPolicies/background-flush-policy.ts

@@ -18,7 +18,7 @@ export class BackgroundFlushPolicy extends FlushPolicyBase {
       'change',
       (nextAppState) => {
         if (
-          this.appState === 'active' &&
+          (this.appState === 'active' || this.appState === 'unknown') &&
           ['inactive', 'background'].includes(nextAppState)
         ) {
           // When the app goes into the background we will trigger a flush