Detection age not always set

[nmichlo]

Describe the bug

Age is not set on all newly added detections.

To Reproduce

Set past_detections_length to some low number, and add more detections than this. The detection age will not be set after being "added" when discarded.

Expected behavior

Even when discarded, the detection age should still be set after being added, because this affects the last_detection.

norfair/norfair/tracker.py

Lines 700 to 715 in 009a1b1

	def _conditionally_add_to_past_detections(self, detection):
	"""Adds detections into (and pops detections away) from `past_detections`
	It does so by keeping a fixed amount of past detections saved into each
	TrackedObject, while maintaining them distributed uniformly through the object's
	lifetime.
	"""
	if self.past_detections_length == 0:
	return
	if len(self.past_detections) < self.past_detections_length:
	detection.age = self.age
	self.past_detections.append(detection)
	elif self.age >= self.past_detections[0].age * self.past_detections_length:
	self.past_detections.pop(0)
	detection.age = self.age
	self.past_detections.append(detection)

Seems like the above lines should always set the detection age. It should also probably assert that the age has not already been set / added to a tracker.

Screenshots or videos
N/A

Environment (please complete the following information):

• OS: [e.g. Ubuntu 20.04]
• Python version: [e.g. 3.9.10]
• Norfair version: [e.g. 1.0.0]

Additional context
N/A