fix error in articles without description

src/components/Header.vue

@@ -29,7 +29,7 @@
     <h2 class="secondary_header" 
         v-if="secondary_header_text.length">{{secondary_header_text}}</h2>
     <span class="header_group_list" 
-          v-if="lemma_group.description.length">{{lemma_group.description}}</span>
+          v-if="lemma_group.description">{{lemma_group.description}}</span>
     <span v-if="$store.state.showInflectionNo">{{lemma_group.inflection_classes}}</span>
     <SplitInf :lemmas="lemmas"/>