fix: promise leak by capturing rejection from getVersion

[alexruzenhack]

Acceptance Criteria

• Resolve promise leak in the wallet start method when using the VersionApi

Related to: HathorNetwork/hathor-wallet-mobile#364

Security Checklist

• Make sure you do not include new dependencies in the project unless strictly necessary and do not include dev-dependencies as production ones. More dependencies increase the possibility of one of them being hijacked and affecting us.

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (29ca737) 64.86% compared to head (1a1ef76) 64.86%.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev     #584   +/-   ##
=======================================
  Coverage   64.86%   64.86%           
=======================================
  Files          67       67           
  Lines        5254     5254           
  Branches     1108     1108           
=======================================
  Hits         3408     3408           
  Misses       1766     1766           
  Partials       80       80           

Files	Coverage Δ
src/new/wallet.js	40.80% <50.00%> (ø)

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[tuliomir]

It's worth taking a look at #579 too, as it also proposes an async wrapper and unit tests around this same method. Link to the relevant code section.