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/resolve/lib/normalize-options.js

@@ -0,0 +1,10 @@
+module.exports = function (x, opts) {
+    /**
+     * This file is purposefully a passthrough. It's expected that third-party
+     * environments will override it at runtime in order to inject special logic
+     * into `resolve` (by manipulating the options). One such example is the PnP
+     * code path in Yarn.
+     */
+
+    return opts || {};
+};