Add comma before "it is illegal"

Co-authored-by: Elena Shmoylova <eshmoylova@users.noreply.github.com>

chapters/inheritance.tex

@@ -472,7 +472,7 @@ \subsection{Modifiers for Array Elements}\label{modifiers-for-array-elements}
   Matrices and general arrays of elements are treated by viewing those as vectors of vectors etc.
 \item
   If a nested modifier is split, the split is propagated to all elements of the nested modifier, and if they are modified by the \lstinline!each! keyword the split is inhibited for those elements.
-  If the nested modifier that is split in this way contains re-declarations that are split it is illegal.
+  If the nested modifier that is split in this way contains re-declarations that are split, it is illegal.
 \end{itemize}
 
 \begin{example}