Fix last element of sidebar being hidden for small screens

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/assets/stylesheets/generic/sidebar.scss

@@ -39,7 +39,7 @@
 
 .nav-sidebar {
   margin-top: 14 + $header-height;
-  margin-bottom: 50px;
+  margin-bottom: 100px;
   transition-duration: .3s;
   list-style: none;
   overflow: hidden;