ADD: hide searche if not logged in (closes #219)

frontend/src/components/Navbar.vue

@@ -38,7 +38,7 @@
         </b-nav-item>
       </b-navbar-nav>
       <b-navbar-nav class="ml-auto">
-        <GlobalSearch/>
+        <GlobalSearch v-if="$store.state.user"/>
         <b-nav-item :active="$store.state.show_sidebar"
                     @click.stop="$store.commit('showSidebar', !$store.state.show_sidebar)">
           <font-awesome-icon :icon="['fas', 'tasks']"/>