add ability to hide missing data from hover tooltip

I have a dataframe column with some missing values which I want to include in hover_data. Is it possible to show the column in the hover tooltip only if there's value for the currently hovered point? The current default behavior is to show col_name=%{customdata[0]} for missing values. I think it would be better to show nothing at all.

import plotly.express as px

df = px.data.gapminder().query("continent=='Oceania'")

df["pop"] = None

fig = px.line(
    df,
    x="year",
    y="lifeExp",
    color="country",
    hover_data=["pop"],
    title="layout.hovermode='closest' (the default)",
)
fig.update_traces(mode="markers+lines")

fig.show()

首先使用 plotly.express.line 和 hover_data 重现提供的 Python 示例，然后跟踪缺失值如何变成 hover tooltip 文本。完成标准是：包含缺失值的点不再显示 hover 列，而已填充的值仍然可见；如果找到相关的测试区域，请为此行为添加或更新覆盖。