fix issue when parameters are empty or the first arg is not an string, closes #49

Author: jfromaniello

lib/url-join.js

@@ -6,6 +6,11 @@
 
   function normalize (strArray) {
     var resultArray = [];
+    if (strArray.length === 0) { return ''; }
+
+    if (typeof strArray[0] !== 'string') {
+      throw new TypeError('Url must be a string. Received ' + strArray[0]);
+    }
 
     // If the first part is a plain protocol, we combine it with the next part.
     if (strArray[0].match(/^[^/:]+:\/*$/) && strArray.length > 1) {