fix: add guard for disposed JCEF browser in sendToWebview (#11897)

* fix: add guard for disposed JCEF browser in sendToWebview

Before calling executeJavaScript, check if the browser is already closed
to prevent NPE propagation from deeper in JCEF. Also broadens the catch
from IllegalStateException to Exception to handle NPE and other errors
that can occur when the browser is in a disposed state.

Fixes #8085, #9159

* fix: add log warning when sending to disposed browser

Log the message type before early-returning on a closed JCEF browser
to aid debugging silent message drops during project disposal.