Check addresses length when getting last submitted name

[fvictorio]

Closes #145.

[coveralls]

Pull Request Test Coverage Report for Build 509

• 1 of 2 (50.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.01%) to 80.1%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
blockchain/contracts/ProofOfPhysicalAddress.sol	1	2	50.0%
<!--	Total:	1	2	50.0%	-->

Totals
Change from base Build 502:	-0.01%
Covered Lines:	977
Relevant Lines:	1193

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💛 - Coveralls