Odd sampling frequency breaks the aligner

[au650680]

Using aligner.py and accelerometer.py to read data from sources with a sampling frequency that is not a multiple of 16 or if the numbers_to_samples is odd too, then after aligning some data may be left in the first key of self.data_map, which leads to batch_size being wrong. This breaks the aligner, since no subsequent package will have that batch_size.

example-shm/src/data/accel/hbk/accelerometer.py

Lines 95 to 104 in ce47244

	def get_batch_size(self) -> Optional[int]:
	"""
	Returns the number of samples in the first available data batch.
	Useful for determining alignment batch size.
	"""
	with self._lock:
	if not self.data_map:
	return None
	first_key = next(iter(self.data_map))
	return len(self.data_map[first_key])