fix. 워닝 수정을 위한 코드 리팩토링

layers/components/layouts/Header.vue

@@ -280,6 +280,7 @@ onMounted(() => {
                   class="nav-item"
                   :class="{
                     'is-hidden':
+                      isMounted &&
                       overflowNam > 0 &&
                       Number(key) >=
                         Object.keys(gnbData?.menus).length - overflowNam,
@@ -331,7 +332,7 @@ onMounted(() => {
                   </Transition>
                 </div>
               </div>
-              <div v-if="overflowNam > 0" class="more">
+              <div v-if="isMounted && overflowNam > 0" class="more">
                 <button class="btn-more">
                   <AtomsIconsOptionHorizontalFill class="mx-auto" />
                   <span class="sr-only">more</span>