Matching of latexcommands inside arguments fails

[mthark]

In case of \begin{enumerate}[label = (\alph*)] and \begin{enumerate}[label = (\arabic*)] resp., the pretty printing process fails with an exception:
Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: -1
at java.base/java.lang.String.substring(String.java:1841)
at latexbreak.LatexBreak.lambda$addLinebreaks$2(LatexBreak.java:367)
at java.base/java.util.Optional.map(Optional.java:265)
at latexbreak.LatexBreak.addLinebreaks(LatexBreak.java:367)
at latexbreak.LatexBreak.process(LatexBreak.java:183)
at latexbreak.LatexBreak.main(LatexBreak.java:117)