URL is sometimes not sent on window activation when KeePass has recently launched

[Aldaviva]

The workaround is usually to activate a different window first and then activate Vivaldi again.

I think this is being caused by the 500 ms debouncing logic, where

1. the previous request went out before KeePass was running or its web server was listening
2. KeePass's web server starts
3. Vivaldi's window is activated, and the extension is informed of this by the external message sent from the Vivaldi first-party extension (custom.js)
4. this extension skips sending the XHR to KeePass because less than 500 ms has elapsed since the last (failed) request went out, and the URL did not change

It's also possible that the active window detection doesn't always work properly. For example, there may be a race condition between the Vivaldi first-party extension sending the Chromium runtime external message to this extension telling it that a window was activated, and this extension's calls to chrome.windows.getCurrent returning the newly activated window. Losing this race would result in the wrong URL being read.