fix(navigation): ignore unknown JS errors when looking for the URL

This should address #841

Ignoring the error and trying again has worked for all of my test cases,
and the error has never occurred more than once in a row.

lib/protractor.js

@@ -907,9 +907,21 @@ Protractor.prototype.get = function(destination, opt_timeout) {
   // At this point, we need to make sure the new url has loaded before
   // we try to execute any asynchronous scripts.
   this.driver.wait(function() {
-    return self.driver.executeScript('return window.location.href;').then(function(url) {
-      return url !== 'about:blank';
-    });
+    return self.driver.executeScript('return window.location.href;').
+        then(function(url) {
+          return url !== 'about:blank';
+        }, function(err) {
+          if (err.code == 13) {
+            // Ignore the error, and continue trying. This is because IE
+            // driver sometimes (~1%) will throw an unknown error from this
+            // execution. See https://github.com/angular/protractor/issues/841
+            // This shouldn't mask errors because it will fail with the timeout
+            // anyway.
+            return false;
+          } else {
+            throw err;
+          }
+        });
   }, timeout * 1000, 'Timed out waiting for page to load');
 
   var assertAngularOnPage = function(arr) {