Return error when the address is an empty string

[dauTT]

Description

closes: #6760

---

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[codecov]

Codecov Report

Merging #6907 into master will decrease coverage by 0.04%.
The diff coverage is 14.28%.

@@            Coverage Diff             @@
##           master    #6907      +/-   ##
==========================================
- Coverage   61.82%   61.78%   -0.05%     
==========================================
  Files         520      520              
  Lines       32129    32147      +18     
==========================================
- Hits        19865    19861       -4     
- Misses      10656    10676      +20     
- Partials     1608     1610       +2     

[alexanderbez]

ACK @dauTT, but we're 100% going to have to fix some tests.

[jgimeno]

Looks good! As @alexanderbez mentioned some tests fail now, should not be a big issue to solve them.

[dauTT]

In many places we do allow to use nil address in a query like in this case:

nil address have actually well define empty string representation:

In the end the tests fails because the unmarshalling of empty string address does not work anymore:

So it seems, after all, not a bad idea to allow empty string in AccAddressFromBech32. What do you think?

[alexanderbez]

AccAddressFromBech32 should return an error if the string is empty. "" is not a valid address.

[dauTT]

Some tests are failing, but I think they are not related to this PR.