Error when parsing case statements with OR operators

[cetfor]

I ran into an interesting error when parsing Bash like this. Notice line 3 where we use logical OR.

while [ true ]; do
    case "$command" in
        "exit" | "quit" | "q")   # issue here
            exit
            ;;
    esac
done

This throws the following error:

ReferenceError: pattern is not defined at Object.anonymous (https://vorpaljs.github.io/bash-parser-playground/bundle.js:8177:27) at Parser.parse (https://vorpaljs.github.io/bash-parser-playground/bundle.js:8382:36) at parse (https://vorpaljs.github.io/bash-parser-playground/bundle.js:7587:22) at HTMLTextAreaElement.parseSource (https://vorpaljs.github.io/bash-parser-playground/bundle.js:3:66) at HTMLTextAreaElement.dispatch (https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js:3:12444) at HTMLTextAreaElement.r.handle (https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js:3:9173)

When you remove the ORs and use a single case everything works.

while [ true ]; do
    case "$command" in
        "q")    # this works fine
            exit
            ;;
    esac
done

This issue happens when using https://vorpaljs.github.io/bash-parser-playground/ but it does not occur when using node-parser. Using node-parser in my own application successfully generates an AST for the first code block shown above.