fix(windows): contextual help chm file has blank pages

[sze2st]

fixes: #15571
These changes fixes the issue of empty subchapters of chapter "contextual help" in windows chm help file.

Build-bot: release:windows

[keymanapp-test-bot]

User Test Results

Test specification and instructions

• ⬜ TEST_CONTEXTUAL_HELP (OPEN)

Results Template

# Test Results

* **TEST_CONTEXTUAL_HELP (OPEN):** notes

Test Artifacts

• Android
  • Keyman for Android apk - build : all tests passed (no artifacts on BuildLevel "build")
  • FirstVoices Keyboards for Android apk - build : all tests passed (no artifacts on BuildLevel "build")
  • FirstVoices Keyboards for Android apk (old PRs) - build : all tests passed (no artifacts on BuildLevel "build")
  • KeyboardHarness apk - build : all tests passed (no artifacts on BuildLevel "build")
  • Keyman for Android apk (old PRs) - build : all tests passed (no artifacts on BuildLevel "build")
  • KMSample1 apk - build : all tests passed (no artifacts on BuildLevel "build")
  • KMSample2 apk - build : all tests passed (no artifacts on BuildLevel "build")
• Developer
  • Keyman Developer - build : all tests passed (no artifacts on BuildLevel "build")
  • Compiler Regression Tests - build : all tests passed (no artifacts on BuildLevel "build")
  • Keyman Developer (old PRs) - build : all tests passed (no artifacts on BuildLevel "build")
  • kmcomp.zip - build : all tests passed (no artifacts on BuildLevel "build")
  • kmcomp.zip (old PRs) - build : all tests passed (no artifacts on BuildLevel "build")
• iOS
  • Keyman for iOS (simulator image) - build : all tests passed (no artifacts on BuildLevel "build")
  • FirstVoices Keyboards for iOS (simulator image) - build : all tests passed (no artifacts on BuildLevel "build")
  • FirstVoices Keyboards for iOS (simulator image) (old PRs) - build : all tests passed (no artifacts on BuildLevel "build")
  • Keyman for iOS (simulator image) (old PRs) - build : all tests passed (no artifacts on BuildLevel "build")
• Keyboards
  • Test Keyboards - build : all tests passed (no artifacts on BuildLevel "build")
• macOS
  • Keyman for macOS - build : all tests passed (no artifacts on BuildLevel "build")
  • Keyman for macOS (old PRs) - build : all tests passed (no artifacts on BuildLevel "build")
• Web
  • KeymanWeb Test Home - build : all tests passed (no artifacts on BuildLevel "build")
• Windows
  • Keyman for Windows
  • FirstVoices Keyboards for Windows
  • FirstVoices Keyboards for Windows (old PRs)
  • Keyman for Windows (old PRs)
  • Text Editor (ARM64)
  • Text Editor (x64)
  • Text Editor (x86)

[sze2st]

User Testing

• TEST_CONTEXTUAL_HELP

• open Keyman for Windows User Guide by double click on keymandesktop.chm
• In content on left hand side expand first chapter "Keyman for Windows 19.0 Help"
• Expand subchapter "Contextual Help"
• click on any of the subchapters of "Contextual Help" (e.g. "set hotkey"): The right hand side should not only come with a headline but with detailed description.
• NOTE: When clicking on a subchapter of "Contextual Help" the focus of the content will change. e.g. when clicking on "set hotkey" will change to subchapter "How To - Set Hotkeys for Keyman, Keyman Keyboards and Windows Languages" of chapter "Getting Started on Windows".
  (Same already happens when using html file instead of chm and is caused by internal linking. This issue is not part of the current fix)

[mcdurdin]

I think this LGTM, although I am not sure why the old code wasn't working?