Add return if delta queue is empty

SubscriptionExecutor now shares 1 delta queue between push, sms, user so we can return if it is empty

src/core/executors/SubscriptionExecutor.ts

@@ -12,6 +12,10 @@ export class SubscriptionExecutor extends ExecutorBase {
   }
 
   processDeltaQueue(): void {
+    if (this._deltaQueue.length === 0) {
+      return;
+    }
+
     const modelSpecificDeltasArrays = this.separateDeltasByModelId();
 
     modelSpecificDeltasArrays.forEach((deltasArray) => {