KaTeX math problem for hard-tab-indented equation with linebreak

[functoreality]

This works correctly:

1. text
    $$\begin{bmatrix} 
        a,b 
    \end{bmatrix}$$

But if we use hard tabs (i.e. \t) instead of spaces for indentation, the equation is not correctly displayed. What's more, if we write the equation in a single line (i.e. no linebreak between two $$'s), it works correctly again, even with hard-tabs.

[iamcco]

bug of markdown-it