Fixing missing navbar on small screens

src/app/header/header.component.html

@@ -4,7 +4,7 @@
             <a href="#" class="navbar-brand">Recipe Book</a>
         </div>
 
-        <div class="collapse navbar-collapse">
+        <div class="navbar-default">
             <ul class="nav navbar-nav">
                 <li><a href="#">Recipes</a></li>
                 <li><a href="#">Shopping List</a></li>