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/cssstyle/lib/properties/borderCollapse.js

@@ -0,0 +1,26 @@
+'use strict';
+
+var parsers = require('../parsers');
+
+var parse = function parse(v) {
+  if (
+    parsers.valueType(v) === parsers.TYPES.KEYWORD &&
+    (v.toLowerCase() === 'collapse' ||
+      v.toLowerCase() === 'separate' ||
+      v.toLowerCase() === 'inherit')
+  ) {
+    return v;
+  }
+  return undefined;
+};
+
+module.exports.definition = {
+  set: function(v) {
+    this._setProperty('border-collapse', parse(v));
+  },
+  get: function() {
+    return this.getPropertyValue('border-collapse');
+  },
+  enumerable: true,
+  configurable: true,
+};