Unchecked runtime.lastError when a page enters back/forward cache

Unchecked runtime.lastError when a page enters back/forward cache

Environment
- Extension: AB Download Manager Browser Integration 1.5.0
- Browser: Microsoft Edge 152.0.4191.66 (macOS, arm64)
- App: AB Download Manager 1.10.4
- Installed via "Load unpacked" (no Edge Add-ons store version available)

Error
Unchecked runtime.lastError: The page keeping the extension port is
moved into back/forward cache, so the message channel is closed.

Steps to reproduce
1. Open several tabs and navigate back/forward so pages enter BFCache
2. Open edge://extensions and check the extension's error log

Expected
The extension should handle the port disconnect caused by Chromium's
BFCache eviction: read chrome.runtime.lastError inside the disconnect
handler (so no unchecked error is logged) and re-establish the port
when the page is restored.

Actual
The disconnect is not handled, so an "Unchecked runtime.lastError"
entry is logged every time a page is moved into BFCache.

Notes
Disabling the Memory Saver / Sleeping Tabs features only reduces the
frequency; BFCache is enabled by default so the error still occurs.
Workaround: toggling the extension off and on restores functionality.