When take_tiled_screenshot returns None, the previous fallback immediately took
a standard element.screenshot() with no spinner check or animation wait, which
produced a blank image that silently became a blank PDF sent to recipients.
Remove the fallback: return None instead, which propagates up through
_get_screenshots() → ReportScheduleScreenshotFailedError → ERROR execution
state with owner notification.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>