Added checks to make sure the specified track exists

Added precondition checks to validate input files and paths to return more informative error messages as per #2

node_modules/jest-util/build/deepCyclicCopy.d.ts

@@ -0,0 +1,12 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+export declare type DeepCyclicCopyOptions = {
+    blacklist?: Set<string>;
+    keepPrototype?: boolean;
+};
+export default function deepCyclicCopy<T>(value: T, options?: DeepCyclicCopyOptions, cycles?: WeakMap<any, any>): T;
+//# sourceMappingURL=deepCyclicCopy.d.ts.map