Up side down question mark at beginning when import MathML

When I try to import mathml file like this:

<?xml version="1.0" encoding="UTF-8"?>
<math xmlns="http://www.w3.org/1998/Math/MathML">
<mtable class="m-equation-square" displaystyle="true" style="display: block; margin-top: 1.0em; margin-bottom: 2.0em">
			<mspace width="6.0em" />
		<mtd columnalign="left">

I always get a “?” at the beginning of the formula (Up side down).

I think it is because it can interpret the mspace properly.

When I open the LibreOffice Math, I found it has empty entry of the first element in the MAXTRIX:

matrix {# {italic "e"^{italic "i" italic "π"} = - italic "1"}}

How could I fix this issue?

It seems, that the mspace element is ignored on import. Therefore the intended rendering effect will not be possible. To get an invisible element at this matrix position (actually an empty string), you can use

<mtd> <mtext /> </mtd>

If you really need a space of 6em, you can use

<mtd> <mphantom> <mtext >mmmmmm </mtext> </mphantom> </mtd>