Return empty margin catalog instead of None with from_dataframe

[hombit]

Bug report

from_dataframe() should assign empty margin catalog instead of None when margin is empty. Originated from this discussion:
#416 (comment)

It looks like it is the similar to #329

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• I have described the situation in which the bug arose, including what code was executed, information about my environment, and any applicable data others will need to reproduce the problem.
• I have included available evidence of the unexpected behavior (including error messages, screenshots, and/or plots) as well as a descriprion of what I expected instead.
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[hombit]

A reproducible example

import pandas as pd
from lsdb import from_dataframe

# Fails
assert from_dataframe(pd.DataFrame({'ra': [1.0], 'dec': [1.0]})).margin is not None