Fix state of label selection on LabelingMenu for sequenceLabeling

Currently labeling two enties with the same label by chosing it from the
autocomplete, didn't work. Labeling the first entity worked, but when you
tried to label a new entity with the same label chosen from the
autocomplete, nothing happened.

frontend/components/tasks/sequenceLabeling/LabelingMenu.vue

@@ -16,7 +16,7 @@
       <v-list-item>
         <v-autocomplete
           ref="autocomplete"
-          :value="selectedLabel"
+          v-model="value"
           :items="labels"
           autofocus
           dense
@@ -92,6 +92,7 @@ export default Vue.extend({
       entity: null as any,
       fromEntity: null as any,
       toEntity: null as any,
+      value: this.selectedLabel
     };
   },
 
@@ -106,6 +107,7 @@ export default Vue.extend({
       // Todo: a bit hacky. I want to fix this problem.
       // https://github.com/vuetifyjs/vuetify/issues/10765
       this.$nextTick(() => {
+        this.value = undefined;
         if (this.$refs.autocomplete) {
           (this.$refs.autocomplete as any).selectedItems = []
         }
@@ -114,9 +116,10 @@ export default Vue.extend({
     },
 
     onLabelSelected(labelId: number) {
+      this.value= labelId;
       this.$emit('click:label', labelId)
       this.close()
     }
   }
 })
-</script>
+</script>