[Bugfix] skip get byte when exporting not migrated code

[yun-yeo]

Summary of changes

close #606

Report of required housekeeping

• Github issue OR spec proposal link
• Wrote tests
• Updated API documentation (client/lcd/swagger-ui/swagger.yaml)
• Added a relevant changelog entry: clog add [section] [stanza] [message]

---

(FOR ADMIN) Before merging

• Added appropriate labels to PR
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)
• Confirm added tests are consistent with the intended behavior of changes
• Ensure all tests pass

[codecov]

Codecov Report

Merging #607 (d9c6696) into main (19b75bf) will increase coverage by 0.01%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##             main     #607      +/-   ##
==========================================
+ Coverage   44.69%   44.71%   +0.01%     
==========================================
  Files         120      120              
  Lines        6967     6969       +2     
==========================================
+ Hits         3114     3116       +2     
  Misses       3614     3614              
  Partials      239      239              

Impacted Files	Coverage Δ
x/wasm/genesis.go	68.00% <66.66%> (+1.33%)	⬆️