Upgrade nuxt to 2.13.0

frontend/layouts/default.vue

@@ -1,7 +1,7 @@
 <template>
     <v-app dark>
         <Navbar />
-        <v-content>
+        <v-main>
             <v-container fill-height>
                 <v-row no-gutters justify="center">
                     <nuxt />
@@ -10,7 +10,7 @@
                     msg
                 }}</v-snackbar>
             </v-container>
-        </v-content>
+        </v-main>
     </v-app>
 </template>
 
@@ -27,7 +27,7 @@ export default {
     mounted() {
         this.$root.$on('toast', (msg, color) => {
             this.msg = msg
-            this.color = color ?? ''
+            this.color = color || ''
             this.toast = true
         })
     },

frontend/layouts/empty.vue

@@ -1,15 +1,11 @@
 <template>
     <v-app>
-        <v-content>
+        <v-main>
             <nuxt />
-        </v-content>
+        </v-main>
     </v-app>
 </template>
 
-<script>
-export default {}
-</script>
-
 <style>
 html {
     overflow-y: auto;