🐛 Fixed malformed URLs crashing the url helper

refs https://github.com/TryGhost/Team/issues/960

- Character like "%%" or "%80" would crash our current url escaping behavior. We consider they aren't valid URLs as the percentages haven't been properly escaped.

core/frontend/helpers/url.js

@@ -6,6 +6,9 @@
 
 const {metaData} = require('../services/proxy');
 const {SafeString} = require('../services/rendering');
+const logging = require('@tryghost/logging');
+const sentry = require('../../shared/sentry');
+const errors = require('@tryghost/errors');
 
 const {getMetaDataUrl} = metaData;
 
@@ -13,7 +16,21 @@ module.exports = function url(options) {
     const absolute = options && options.hash.absolute && options.hash.absolute !== 'false';
     let outputUrl = getMetaDataUrl(this, absolute);
 
-    outputUrl = encodeURI(decodeURI(outputUrl));
+    try {
+        outputUrl = encodeURI(decodeURI(outputUrl));
+    } catch (err) {
+        // Happens when the outputURL contains an invalid URI character like "%%" or "%80"
+
+        // Send the error not to be blind to these
+        const error = new errors.IncorrectUsageError({
+            message: `The url "${outputUrl}" couldn't be escaped correctly`,
+            err: err
+        });
+        sentry.captureException(error);
+        logging.error(error);
+
+        return new SafeString('');
+    }
 
     return new SafeString(outputUrl);
 };

test/unit/frontend/helpers/url.test.js

@@ -9,7 +9,7 @@ const url = require('../../../../core/frontend/helpers/url');
 const urlService = require('../../../../core/server/services/url');
 const api = require('../../../../core/server/api');
 
-describe('{{url}} helper', function () {
+describe.only('{{url}} helper', function () {
     let rendered;
 
     beforeEach(function () {
@@ -267,6 +267,12 @@ describe('{{url}} helper', function () {
             should.exist(rendered);
             rendered.string.should.equal('/?foo=space%20bar');
         });
+
+        it('should an empty string when we can\'t parse a string', function () {
+            rendered = url.call({url: '/?foo=space%%bar', label: 'Baz', slug: 'baz', current: true});
+            should.exist(rendered);
+            rendered.string.should.equal('');
+        });
     });
 
     describe('with subdir', function () {