LIL-237. Clear empty section

apps/course/templates/course/course.html

@@ -205,7 +205,7 @@
     </div>
   </div>
 {% endfor %}
-{% if user.is_authenticated %}
+{% if user.is_authenticated and course.lessons.exists %}
 <div class="section">
   <div class="section__center center center_sm">
     <div class="lessons">
@@ -262,11 +262,13 @@
   </div>
 </div> {% endcomment %}
 {% endif %}
+{% if course.gallery %}
 <div class="section section_gradient">
   <div class="section__center center center_sm">
     {% include "course/content/gallery.html" with results=True %}
   </div>
 </div>
+{% endif %}
 <div 
   class="course course_promo"
   style="background-image: url({% if course.cover %}{{ course.cover.image.url }}{% else %}{% static 'img/no_cover.png' %}{% endif %});"