Gaiacli should not panic when user just presses enter during Y/n confirmation

[haasted]

Addressing the issue encountered here: e-money/em-ledger#1

If the user does not enter a character in response to the CLI query confirm transaction before signing and broadcasting [y/N]: gaiacli will crash with a panic.

• Linked to github-issue with discussion and accepted design OR link to spec that describes this work.
• Wrote tests
• Updated relevant documentation (docs/)
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the github PR explorer

[codecov]

Codecov Report

Merging #4919 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4919      +/-   ##
==========================================
+ Coverage   53.67%   53.68%   +0.01%     
==========================================
  Files         272      272              
  Lines       17052    17052              
==========================================
+ Hits         9152     9154       +2     
+ Misses       7210     7208       -2     
  Partials      690      690

[codecov]

Codecov Report

Merging #4919 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4919      +/-   ##
==========================================
+ Coverage   53.67%   53.68%   +0.01%     
==========================================
  Files         272      272              
  Lines       17052    17052              
==========================================
+ Hits         9152     9154       +2     
+ Misses       7210     7208       -2     
  Partials      690      690

[fedekunze]

ACK. Please add a bugfix entry on the changelog.md

[alexanderbez]

ACK -- thanks @haasted :)