Error: Error invoking postMessage: Java exception was raised during method invocation

## Error

```
Error invoking postMessage: Java exception was raised during method invocation
```

## Stack trace

```
iabjs://navigation_performance_logger_android:1 in sendDataToNative
iabjs://navigation_performance_logger_android:1 in sendBeforeUnloadMessage
iabjs://navigation_performance_logger_android:1 in window._handleBrowserPreparingToClose
:1
:1
```

## Tracking Details
- **Project**: exercism-js
- **Sentry**: [Error: Error invoking postMessage: Java exception was raised during method invocation](https://thalamus-ai.sentry.io/issues/144051814/)
- **Culprit**: sendDataToNative(iabjs://navigation_performance_logger_android)
- **First seen:** Aug 31, 2026

Start with the linked Sentry issue and the stack trace entry points: sendDataToNative, sendBeforeUnloadMessage, and window._handleBrowserPreparingToClose. Trace the Android postMessage path and determine how to reproduce the Java exception; done means the error is explained and the failing navigation-close path no longer reports it.

Written by the indexing model from the issue text.