Check that addressIndex is within bounds

[fvictorio]

Closes #134.

[coveralls]

Pull Request Test Coverage Report for Build 431

• 4 of 4 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.06%) to 79.336%

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Totals
Change from base Build 429:	0.06%
Covered Lines:	963
Relevant Lines:	1188

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💛 - Coveralls

[fvictorio]

@phahulin This closed the last issue related with the audit. I think the next step is for the auditors to check the fixes, am I right?

[phahulin]

@fvictorio yes, I left comments for them with links to this and two other PRs.