R4R: Fix setting tx hash when nil

[alexanderbez]

closes: #3585

---

• Targeted PR against correct branch (see CONTRIBUTING.md)

• Linked to github-issue with discussion and accepted design OR link to spec that describes this work.

• Wrote tests

• Updated relevant documentation (docs/)

• Added entries in PENDING.md with issue #

• rereviewed Files changed in the github PR explorer

---

For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[alessio]

ACK

[codecov]

Codecov Report

Merging #3591 into develop will increase coverage by 0.02%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           develop   #3591      +/-   ##
==========================================
+ Coverage    61.47%   61.5%   +0.02%     
==========================================
  Files          186     186              
  Lines        13978   13981       +3     
==========================================
+ Hits          8593    8599       +6     
+ Misses        4838    4835       -3     
  Partials       547     547

[cwgoes]

ACK