add fourLayer

src/store/modules/breadcrumb.js

     visible: {
       firstLayer: true,
       secondLayer: false,
-      thirdLayer: false
+      thirdLayer: false,
+      fourLayer: false
     }
   },
   mutations: {
           state.visible = {
             firstLayer: true,
             secondLayer: false,
-            thirdLayer: false
+            thirdLayer: false,
+            fourLayer: false
           }
           break
         case 2:
           state.visible = {
             firstLayer: false,
             secondLayer: true,
-            thirdLayer: false
+            thirdLayer: false,
+            fourLayer: false
           }
           break
         case 3:
           state.visible = {
             firstLayer: false,
             secondLayer: false,
-            thirdLayer: true
+            thirdLayer: true,
+            fourLayer: false
+          }
+          break
+        case 4:
+          state.visible = {
+            firstLayer: false,
+            secondLayer: false,
+            thirdLayer: false,
+            fourLayer: true
           }
           break
       }