fix(kanban): make sure only one task input field can be visible at the same time

frontend/src/components/project/views/ProjectKanban.vue

@@ -165,7 +165,7 @@
 											class="bucket-footer"
 										>
 											<div
-												v-if="showNewTaskInput[bucket.id]"
+												v-if="showNewTaskInput === bucket.id"
 												class="field"
 											>
 												<div
@@ -371,7 +371,7 @@ const bucketToDelete = ref(0)
 const bucketTitleEditable = ref(false)
 
 const newTaskText = ref('')
-const showNewTaskInput = ref<{ [id: IBucket['id']]: boolean }>({})
+const showNewTaskInput = ref<IBucket['id'] | null>(null)
 
 const newBucketTitle = ref('')
 const showNewBucketInput = ref(false)
@@ -612,7 +612,9 @@ function toggleShowNewTaskInput(bucketId: IBucket['id']) {
 	if (loading.value || taskLoading.value) {
 		return
 	}
-	showNewTaskInput.value[bucketId] = !showNewTaskInput.value[bucketId]
+	showNewTaskInput.value = showNewTaskInput.value === bucketId 
+		? null
+		: bucketId
 	newTaskInputFocused.value = false
 }