The render gate for an empty placeholder's fill checked only
s.fill.is_none(). A quick style that sets a style reference without
an explicit fill left s.fill as None, so the gate skipped the fill
even though the shape had been formatted — the style only appeared
after text was added.
The gate now also checks s.line and s.style: if any of the three has
a local override, the placeholder is considered formatted and the
fill is drawn. A truly unformatted empty placeholder still shows the
dashed outline and prompt.