A VectorDrawable should consist of at least one <path> tag defining a shape

<vector xmlns:android="<http://schemas.android.com/apk/res/android>"
    android:width="24dp"
    android:height="24dp"
    android:viewportWidth="24.0"
    android:viewportHeight="24.0">
    <path
        android:fillColor="#FF000000"
        android:pathData="M0,24 l12,-24 l12,24 z"/>
</vector>

This would produce a black triangle: