Make the visibility of the Alert indirect

src/components/AlertMessage.vue

@@ -18,15 +18,15 @@ import { Component, Prop, Vue } from "vue-facing-decorator";
 export default class AlertMessage extends Vue {
   @Prop alertTitle = "";
   @Prop alertMessage = "";
+  isAlertVisible = this.alertMessage;
 
   public onClickClose() {
-    this.alertTitle = "";
+    this.isAlertVisible = false;
-    this.alertMessage = "";
   }
 
   public computedAlertClassNames() {
     return {
-      hidden: !this.alertMessage,
+      hidden: !this.isAlertVisible,
       "dismissable-alert": true,
       "bg-slate-100": true,
       "p-5": true,