Changed implementation of FieldsArray to accept passInstance instead of pool, to check frozen instance

src/utils.ts

@@ -1,3 +1,6 @@
+import * as Messages from "./messages";
+import type Bundle from "./Bundle";
+
 /**
  * Acts as a wrapper for converting date to W3C string
  * @param date
@@ -105,3 +108,9 @@ export function cloneRecursive(object: Object) {
 
 	return objectCopy;
 }
+
+export function assertUnfrozen(instance: InstanceType<typeof Bundle>) {
+	if (instance.isFrozen) {
+		throw new Error(Messages.BUNDLE.CLOSED);
+	}
+}