Add sanity check to avoid sending empty topology to SDX-LC

[italovalcy]

This pull request adds a sanity check to avoid sending empty topology to SDX-LC when it is pulling for the topology.

[coveralls]

Pull Request Test Coverage Report for Build 10966224011

Details

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.09%) to 78.413%

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Files with Coverage Reduction	New Missed Lines	%
main.py	1	73.53%

Totals
Change from base Build 10930191068:	-0.09%
Covered Lines:	494
Relevant Lines:	630

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💛 - Coveralls