Two-dimensional matrices with more than two columns not rendering

[ouss1002]

Describe the bug
When trying to render a matrix with three columns or more, the rendering fails with the exception java.lang.NullPointerException: Cannot invoke "java.util.List.get(int)" because the return value of "java.util.List.get(int)" is null at net.sourceforge.plantuml.math.ASCIIMathTeXImg.AMTparseExpr(ASCIIMathTeXImg.java:938)

To Reproduce
1- Create a matrix (at least two rows) with three columns or more
2- Wrap it inside of a @startmath ... @endmath block
3- Render the matrix.

Example:

@startmath
H = [[1,2,3],[4,5,6]]
@endmath

Expected behavior
The matrix renders correctly, regardless of the number of rows/columns.

Actual behavior
A java.lang.NullPointerException is thrown, and the rendering is buggy/faulty for the matrix

Screenshots
Here are the results with their corresponding matrix code:

The problem only arises if the matrix has at least two rows and three columns !

Desktop:

OS: Windows server 2019
Browser chrome

Additional context
The matrices used to render correctly back in the version V1.2021.7 where the javascript engine used to be the one that renders the matrices.
This is a regression as noted on the PlantUML website regarding potential regressions post-migration into Java in V1.2021.8

PlantUML version : 1.2024.3

[ouss1002]

Thank you very much @The-Lum for fixing the the issue !
I have a question, will this fix be part of the next release ? ping @arnaudroques

Regards,
Oussama