Fix npm build

Author: spinn

package-lock.json

@@ -2,7 +2,7 @@
   "name": "@ditdot-dev/vue-flow-form",
   "author": "DITDOT",
   "description": "Create conversational conditional-logic forms with Vue.js.",
-  "version": "2.3.0",
+  "version": "2.3.1",
   "private": false,
   "scripts": {
     "serve": "vue-cli-service serve",

package.json

@@ -66,7 +66,7 @@
 
     beforeMount() {
       const 
-        size = this.question.max ?? 5,
+        size = this.question.max || 5,
         numOptions = Math.min(Math.max(size, 1), 10)
     
       if (!this.question.options.length) {