fix(web): don't crash if second transform is null

[ermshiperete]

Fixes: #12494

User Testing

TEST_NOCRASH: follow the steps outlined in #12494 and verify that the crash no longer happens

[keymanapp-test-bot]

User Test Results

Test specification and instructions

• 🟥 TEST_NOCRASH (FAILED) (notes)

Retesting Template

@keymanapp-test-bot retest TEST_NOCRASH

Test Artifacts

• Android
  • Keyman for Android apk
  • FirstVoices for Android 16.0 apk
  • FirstVoices Keyboards for Android apk
  • KeyboardHarness apk
  • Keyman for Android 16.0 apk
  • KMSample1 apk
  • KMSample2 apk
• Developer
  • Keyman Developer
  • Compiler Regression Tests
  • kmcomp.zip
• iOS
  • Keyman for iOS (simulator image)
  • FirstVoices Keyboards for iOS (simulator image)
  • TestFlight internal PR build version - 18.0.163 (0.12860.12498)
• Keyboards
  • Test Keyboards
• Web
  • KeymanWeb Test Home
• Windows
  • Keyman for Windows
  • FirstVoices Keyboards for Windows
  • Text Editor (32 bit)
  • Text Editor (64 bit)

[dinakaranr]

Test Results

I tested this issue with the attached "18.0.163-alpha-test-12860" build on the Andoird 14. Here is my observation.

• TEST_NOCRASH (failed):

1. Open the keyman app in the Android mobile app.
2. Added EuroLatin keyboard.
3. Added a sentence.
4. Added letters in this order.
5. Longpress g --> g̃,
6. Longpress h --> ḥ,
7. Longpress j --> ĵ,
8. Flick down on c --> ',
9. Flick down on v --> ",
10. Here, an Error appeared.
    Please take a look at the attached video file(Android14_Keyman18.0.163-Alpha-Test-12860). Thank you.
    https://github.com/user-attachments/assets/9cafa3da-bd60-4ddf-9fad-2e4164d29590
    I tested this issue on the Android mobile. Please let me know where to test this issue in the web version. Thank you.

[darcywong00]

I got the same error. Here's the console log

       Failed to load resource: net::ERR_FILE_NOT_FOUND
@keymanapp/keyman/web/src/engine/predictive-text/worker-thread/src/main/correction/distance-modeler.ts:155 Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'deleteLeft')
    at _SearchNode.buildDeletionEdges (@keymanapp/keyman/web/src/engine/predictive-text/worker-thread/src/main/correction/distance-modeler.ts:155:20)
    at @keymanapp/keyman/web/src/engine/predictive-text/worker-thread/src/main/correction/distance-modeler.ts:489:28
    at Array.map (<anonymous>)
    at _SearchSpace.addInput (@keymanapp/keyman/web/src/engine/predictive-text/worker-thread/src/main/correction/distance-modeler.ts:488:39)
    at ContextTracker.attemptMatchContext (@keymanapp/keyman/web/src/engine/predictive-text/worker-thread/src/main/correction/context-tracker.ts:487:37)
    at _ContextTracker.analyzeState (@keymanapp/keyman/web/src/engine/predictive-text/worker-thread/src/main/correction/context-tracker.ts:679:37)
    at @keymanapp/keyman/web/src/engine/predictive-text/worker-thread/src/main/predict-helpers.ts:185:48
    at Generator.next (<anonymous>)
    at blob:null/158e62a8-81fe-4436-9c40-0d5446118914:49:63
    at new Promise (<anonymous>)

[jahorton]

I think this is a case where it's more important to examine why a null is appearing there in the first place. I'm looking into it.

[ermshiperete]

Superseded by #12864