Add parent to self.add

Since the default value for `UUID` is `None`, we can safely
avoid unnecessarily checking if `UUID` exists.

GTG/core/tasks.py

@@ -752,10 +752,7 @@ def new(self, title: str = None, parent: UUID = None) -> Task:
         task = Task(id=tid, title=title)
         task.date_added = Date.now()
 
-        if parent:
-            self.add(task, parent)
-        else:
-            self.add(task)
+        self.add(task, parent)
 
         return task