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/uri-js/src/schemes/https.ts

@@ -0,0 +1,11 @@
+import { URISchemeHandler, URIComponents, URIOptions } from "../uri";
+import http from "./http";
+
+const handler:URISchemeHandler = {
+	scheme : "https",
+	domainHost : http.domainHost,
+	parse : http.parse,
+	serialize : http.serialize
+}
+
+export default handler;