fix(tasks): make sure tasks show up if their parent task is not available in the current view

Related https://github.com/go-vikunja/frontend/issues/136
Related https://community.vikunja.io/t/subtasks-are-hidden-when-parent-tasks-are-moved/1911

src/views/project/ProjectList.vue

@@ -179,7 +179,23 @@ watch(
 		if (projectId < 0) {
 			return
 		}
-		tasks.value = tasks.value.filter(t => typeof t.relatedTasks?.parenttask === 'undefined')
+		const tasksById = {}
+		tasks.value.forEach(t => tasksById[t.id] = true)
+
+		tasks.value = tasks.value.filter(t => {
+			if (typeof t.relatedTasks?.parenttask === 'undefined') {
+				return true
+			}
+
+			// If the task is a subtask, make sure the parent task is available in the current view as well
+			for (const pt of t.relatedTasks.parenttask) {
+				if(typeof tasksById[pt.id] === 'undefined') {
+					return true
+				}
+			}
+
+			return false
+		})
 	},
 )