Fix the flag processing of NFTokenModify

[tequdev]

High Level Overview of Change

#5048 (comment)

Context of Change

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (non-breaking change that only restructures code)
• Performance (increase or change in throughput and/or latency)
• Tests (you added tests for code that already exists, or your new feature included in this PR)
• Documentation update
• Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• Release

API Impact

• Public API: New feature (new methods and/or new fields)
• Public API: Breaking change (in general, breaking changes should only impact the next api_version)
• libxrpl change (any change that may affect libxrpl or dependents of libxrpl)
• Peer protocol change (must be backward compatible or bump the peer protocol version)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.0%. Comparing base (ff8b9aa) to head (379d034).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #5246     +/-   ##
=========================================
- Coverage     78.0%   78.0%   -0.0%     
=========================================
  Files          789     789             
  Lines        66953   66955      +2     
  Branches      8107    8110      +3     
=========================================
- Hits         52218   52215      -3     
- Misses       14735   14740      +5     

Files with missing lines	Coverage Δ
src/xrpld/app/tx/detail/NFTokenModify.cpp	100.0% <100.0%> (ø)

... and 2 files with indirect coverage changes

[shawnxie999]

left a few nits - otherwise looks good

[shawnxie999]

left a few nits - otherwise looks good

[shawnxie999]

@tequdev seems like some NFT tests are failing due to wrong count

[shawnxie999]

looks good. @tequdev do you think this ready to merge?

[tequdev]

looks good. @tequdev do you think this ready to merge?

yes, ready to merge.