:bug: checking for hero before loading

vue-theme/src/pages/list.vue

                 router-link(:to="`/${type}/${post.slug}`")
                     p {{post.featured}}
                     img(v-if="post.featured" :src="post.featured" alt="post thumbnail")
-                    img(v-else-if="JSON.parse(post.hero).url" :src="getThumbnailFromYt(JSON.parse(post.hero).url)" alt="post thumbnail from YouTube")
+                    img(v-else-if="post.hero && JSON.parse(post.hero).url" :src="getThumbnailFromYt(JSON.parse(post.hero).url)" alt="post thumbnail from YouTube")
                     p(v-else-if="post.hero") ERROR: {{ post.hero }}
                     p(v-else) ERROR: no thumbnail