prevented deletion of tasks with subtasks

task/src/main/java/de/srsoftware/umbrella/task/SqliteDb.java

@@ -112,6 +112,11 @@ CREATE TABLE IF NOT EXISTS {0} (
 	@Override
 	public void delete(Task task) throws UmbrellaException {
 		try {
+			var rs = select("count(*)").from(TABLE_TASKS).where(PARENT_TASK_ID,equal(task.id())).exec(db);
+			long count = 0;
+			if (rs.next()) count = rs.getLong(1);
+			rs.close();
+			if (count>0) throw new UmbrellaException("Task \"{0}\" has child tasks and thus cannot be deleted!",task.name());
 			Query.delete().from(TABLE_TASKS).where(ID,equal(task.id())).execute(db);
 			Query.delete().from(TABLE_TASKS_USERS).where(TASK_ID,equal(task.id())).execute(db);
 		} catch (SQLException e) {

web/src/main/resources/web/css/default.css

@@ -132,8 +132,8 @@ li.task > button{
     display: none;
 }
 
-li.task:hover{
-    padding: 15px 0;
+li.task{
+    padding: 5px 0;
 }
 
 li.task:hover > button{