Fix error when summary contains entry without ref

lib/models/__tests__/summary.js

@@ -8,11 +8,18 @@ describe('Summary', function() {
             articles: [
                 {
                     title: 'My First Article',
-                    path: 'README.md'
+                    ref: 'README.md'
                 },
                 {
                     title: 'My Second Article',
-                    path: 'article.md'
+                    ref: 'article.md'
+                },
+                {
+                    title: 'Article without ref'
+                },
+                {
+                    title: 'Article with absolute ref',
+                    ref: 'https://google.fr'
                 }
             ]
         },
@@ -33,7 +40,7 @@ describe('Summary', function() {
             var part = summary.getByLevel('1');
 
             expect(part).toBeDefined();
-            expect(part.getArticles().size).toBe(2);
+            expect(part.getArticles().size).toBe(4);
         });
 
         it('can return a Part (2)', function() {
@@ -66,6 +73,12 @@ describe('Summary', function() {
             expect(article).toBeDefined();
             expect(article.getTitle()).toBe('My Second Article');
         });
+
+        it('return undefined if not found', function() {
+            var article = summary.getByPath('NOT_EXISTING.md');
+
+            expect(article).toBeFalsy();
+        });
     });
 
     describe('toText', function() {

lib/models/summary.js

@@ -74,7 +74,12 @@ Summary.prototype.getByLevel = function(level) {
 */
 Summary.prototype.getByPath = function(filePath) {
     return this.getArticle(function(article) {
-        return (LocationUtils.areIdenticalPaths(article.getPath(), filePath));
+        var articlePath = article.getPath();
+
+        return (
+            articlePath &&
+            LocationUtils.areIdenticalPaths(articlePath, filePath)
+        );
     });
 };