fix: blinking previewer

frontend/src/store/index.js

@@ -23,7 +23,8 @@ const state = {
   show: null,
   showShell: false,
   showMessage: null,
-  showConfirm: null
+  showConfirm: null,
+  previewMode: false
 }
 
 export default new Vuex.Store({

frontend/src/store/mutations.js

@@ -82,6 +82,9 @@ const mutations = {
   resetClipboard: (state) => {
     state.clipboard.key = ''
     state.clipboard.items = []
+  },
+  setPreviewMode(state, value) {
+    state.previewMode = value
   }
 }