Created attachment 176646 [details]
munderover_bug.zip

Hello there. I'm writing this issue on behalf of ONLYOFFICE DocumentServer team (https://github.com/ONLYOFFICE/DocumentServer)

During the development of our product, we think we found some problems with rendering formulas with <munderover> and <munder> tag in MathML

We got a sample file, named `MUNDEROVER_without_style.odt` with this content in `Object 1/content.xml` file:

```
<?xml version="1.0" encoding="UTF-8"?>
<math display="block" xmlns="http://www.w3.org/1998/Math/MathML">
	<semantics>
		<mrow>
			<munderover>
				<mo stretchy="false">∫</mo>
				<mstyle mathcolor="red">
					<mn>0</mn>
				</mstyle>
				<mn>1</mn>
			</munderover>
			<mstyle mathcolor="green">
				<mi>a</mi>
			</mstyle>
		</mrow>		
	</semantics>
</math>
```

Opening this file in LibreOffice we got ∫ with two limits - 0 is underscript and 1 is overscript
This files renders correctly (See left part of screenshot in attachment)

But as soon as we try to add color to overscript (making XML file like this, only adding <mstyle mathcolor="blue"> around <mn>1</mn> - we got incorrect file render (see right part of attached screenshot)

```
<?xml version="1.0" encoding="UTF-8"?>
<math display="block" xmlns="http://www.w3.org/1998/Math/MathML">
	<semantics>
		<mrow>
			<munderover>
				<mo stretchy="false">∫</mo>
				<mstyle mathcolor="red">
					<mn>0</mn>
				</mstyle>
				<mstyle mathcolor="blue">
					<mn>1</mn>
				</mstyle>
			</munderover>
			<mstyle mathcolor="green">
				<mi>a</mi>
			</mstyle>
		</mrow>		
	</semantics>
</math>
```
In that case, LibreOffice renders this file with both 0 and 1 in overscript

We think it has something to do with the conversion of this formula to StarMath

The file without style has this StarMath style (copied from opened Libreoffice: 
> { int csup 1 csub color red 0 color green a }

File with style has this StarMath:
> { int csup color blue 1 csub color red 0 color green a }

Seems that one pair of quotes is missing

If we change StarMath of second file to:
> { int csup {color blue 1} csub color red 0 color green a }

We got correct integral with both underscript and overscript  and with the correct color

My Eniroment:
Kubuntu 20.04
LibreOffice flatpak 7.2.3.2