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/jsdom/lib/jsdom/living/generated/CloseEventInit.js

@@ -0,0 +1,58 @@
+"use strict";
+
+const conversions = require("webidl-conversions");
+const utils = require("./utils.js");
+
+const EventInit = require("./EventInit.js");
+
+module.exports = {
+  convertInherit(obj, ret, { context = "The provided value" } = {}) {
+    EventInit.convertInherit(obj, ret, { context });
+
+    {
+      const key = "code";
+      let value = obj === undefined || obj === null ? undefined : obj[key];
+      if (value !== undefined) {
+        value = conversions["unsigned short"](value, { context: context + " has member code that" });
+
+        ret[key] = value;
+      } else {
+        ret[key] = 0;
+      }
+    }
+
+    {
+      const key = "reason";
+      let value = obj === undefined || obj === null ? undefined : obj[key];
+      if (value !== undefined) {
+        value = conversions["USVString"](value, { context: context + " has member reason that" });
+
+        ret[key] = value;
+      } else {
+        ret[key] = "";
+      }
+    }
+
+    {
+      const key = "wasClean";
+      let value = obj === undefined || obj === null ? undefined : obj[key];
+      if (value !== undefined) {
+        value = conversions["boolean"](value, { context: context + " has member wasClean that" });
+
+        ret[key] = value;
+      } else {
+        ret[key] = false;
+      }
+    }
+  },
+
+  convert(obj, { context = "The provided value" } = {}) {
+    if (obj !== undefined && typeof obj !== "object" && typeof obj !== "function") {
+      throw new TypeError(`${context} is not an object.`);
+    }
+
+    const ret = Object.create(null);
+    module.exports.convertInherit(obj, ret, { context });
+    return ret;
+  }
+};