fix: catch correct DoesNotExist in HistoricReverseOneToOneDescriptor.…

[awais786]

Closes #1588

Django's ReverseOneToOneDescriptor.get catches self.related.related_model.DoesNotExist, but when HistoricDescriptorMixin.get_queryset() returns a queryset over the historical model (e.g. HistoricalB instead of B), only the historical model's DoesNotExist matches. Override get in HistoricReverseOneToOneDescriptor to catch queryset.model.DoesNotExist so that hasattr/getattr on a missing reverse OneToOne returns False/None instead of raising.

Adds a regression test to HistoricOneToOneFieldTest covering the missing-relation case.

from onkol.apps.users.models import A
from django.utils.timezone import now

# Create object
a = A.objects.create()

# Get historical version at current time
historic_a = a.history.as_of(now())

# Assertions
assert not hasattr(a, 'b')
assert not hasattr(historic_a, 'b')

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

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• I have run the pre-commit run command to format and lint.
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