fix(developer): use 'N' for nomatch store debug strings (regression in #12107)

[mcdurdin]

Fixes a regression arising from #12107 in debug store strings.

Three sets of eyes -- developer and two code reviewers and we still managed to miss this!

Relates-to: #12623 Relates-to: #12107

@keymanapp-test-bot skip

[keymanapp-test-bot[bot]]

User Test Results

Test specification and instructions

User tests are not required

Test Artifacts

• Developer
  • Keyman Developer
  • Compiler Regression Tests
  • kmcomp.zip
• Keyboards
  • Test Keyboards

[darcywong00]

Could you tweak the PR description? :smile: So we can understand the changelog without having to lookup #12107

[keyman-server]

Changes in this pull request will be available for download in Keyman version 18.0.137-alpha