Delete link in head and add navbar-toggler-icon class

templates/sidenav.html

 <div class="container-fluid sidebar col-xs-12 col-sm-12 col-md-3 col-lg-3">
   <nav class="smalltopics no-background navbar navbar-expand-lg navbar-light bg-white p-0 fixed">
     <label class="side-toggler" for="menu-toggle">
-      <a class="btn btn-lg outline-primary text-primary navbar-toggler chevron" data-toggle="collapse" data-target="#navbarSupportedTopicsContent" aria-controls="navbarSupportedTopicsContent" aria-expanded="false" aria-label="Toggle navigation">
-        <span class="oi oi-chevron-top chevron-up"></span>
-        <span class="oi oi-chevron-bottom chevron-down"></span>
+      <a class="btn btn-lg outline-primary text-primary navbar-toggler" data-toggle="collapse" data-target="#navbarSupportedTopicsContent" aria-controls="navbarSupportedTopicsContent" aria-expanded="false" aria-label="Toggle navigation">
+        <span class="navbar-toggler-icon"></span>
       </a>
     </label>
     <input type="checkbox" id="menu-toggle"/>