With its player left on Auto, a monitor with go2rtc enabled had
selectNextPlayer() pick go2rtc_webrtc first, and with ZM_GO2RTC_PATH
empty select_go2rtc() then alerted "ZM_GO2RTC_PATH is empty", on the
montage for every such monitor, although nobody had chosen go2rtc.
The fallback chain already skipped go2rtc for a monitor without it
enabled; skip it when ZM_GO2RTC_PATH is empty too. A monitor or browser
that chose go2rtc reaches select_go2rtc() directly and still gets the
alert.
A node test drives selectPlayer() through the restart chain for Auto
without a path, Auto with one, and go2rtc chosen explicitly.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>