[Bugfix] Fix market swap handler to properly treat zero spread case

[yun-yeo]

Summary of changes

Current market handler crash when it meets zero tobin tax denom(not possible, under columbus-3). This release will prevent crash for the swap between zero tobin tax denoms.

Report of required housekeeping

• Github issue OR spec proposal link
• Wrote tests
• Updated relevant documentation (docs/)
• Added a relevant changelog entry: clog add [section] [stanza] [message]

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(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 #336 into develop will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop     #336      +/-   ##
===========================================
+ Coverage    71.26%   71.29%   +0.02%     
===========================================
  Files           75       75              
  Lines         3644     3647       +3     
===========================================
+ Hits          2597     2600       +3     
  Misses         901      901              
  Partials       146      146              

[dokwon]

LGTM