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/@babel/generator/lib/generators/template-literals.js

@@ -0,0 +1,33 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.TaggedTemplateExpression = TaggedTemplateExpression;
+exports.TemplateElement = TemplateElement;
+exports.TemplateLiteral = TemplateLiteral;
+
+function TaggedTemplateExpression(node) {
+  this.print(node.tag, node);
+  this.print(node.typeParameters, node);
+  this.print(node.quasi, node);
+}
+
+function TemplateElement(node, parent) {
+  const isFirst = parent.quasis[0] === node;
+  const isLast = parent.quasis[parent.quasis.length - 1] === node;
+  const value = (isFirst ? "`" : "}") + node.value.raw + (isLast ? "`" : "${");
+  this.token(value);
+}
+
+function TemplateLiteral(node) {
+  const quasis = node.quasis;
+
+  for (let i = 0; i < quasis.length; i++) {
+    this.print(quasis[i], node);
+
+    if (i + 1 < quasis.length) {
+      this.print(node.expressions[i], node);
+    }
+  }
+}