fix(course): fix non resolved lessons

views/course.pug

@@ -10,16 +10,18 @@ block content
         ul
           li
             a.active(href=`/courses/${course.fields.slug}`) Course overview
-          each lesson in course.fields.lessons
-            li
-              a(href=`/courses/${course.fields.slug}/lessons/${lesson.fields.slug}`) #{lesson.fields.title}
+          each l in course.fields.lessons
+            if l.fields
+              li
+                a(href=`/courses/${course.fields.slug}/lessons/${l.fields.slug}`) #{l.fields.title}
     section.wrapper-with-sidebar__content
       h1= course.fields.title
 
       if lesson
         +lesson(lesson)
         if lessonIndex + 1< lessons.length
-          a.cta(href=`/courses/${course.fields.slug}/lessons/${lessons[lessonIndex + 1].fields.slug}`) View next lesson
+          if lessons[lessonIndex + 1].fields
+            a.cta(href=`/courses/${course.fields.slug}/lessons/${lessons[lessonIndex + 1].fields.slug}`) View next lesson
       else
         p !{helpers.markdown(course.fields.description)}
         a.cta(href=`/courses/${course.fields.slug}/lessons/${course.fields.lessons[0].fields.slug}`) Start course

views/mixins/_lessonModuleCodeSnippet.pug

@@ -19,3 +19,4 @@ mixin lessonModuleCodeSnippet(module)
       code.ruby= module.fields.ruby
     pre.lesson-module-code__swift
       code.swift= module.fields.swift
+