\ddot 无法与使用会议提供的模板的 \mathbf 一起使用

Question

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\makeatother

我正在使用会议提供的 overleaf 模板，但这只会给我粗体，而字母上方没有点

$\bf \ddot{u},~\dot{u}, ~u$
$\mathbf{\ddot{u}}$

它有效，如果

$\ddot{u}$