Null Dereference Discovered from ANTLR3 Generated Code in NCalc's NCalcParser

I posted a discussion in ANTLR4 about ANTLR3 and wanted to make sure that this repo is aware of the null dereference discovery. You can see the description of the issue in the link below and would like to see if any updates are scheduled to address this:

- https://github.com/antlr/antlr4/discussions/3886#discussion-4388462

Thanks!

Start by reading the linked ANTLR4 discussion and then inspect the generated NCalcParser code referenced in the title. The issue does not identify a file, test, proposed change, or acceptance criteria, so the desired fix and definition of done would need to be established before implementation.

Written by the indexing model from the issue text.