Give a non-normative reason for not allowing 'array()' or '{}'

The new formulation works better as a separate paragraph.

chapters/arrays.tex

@@ -555,8 +555,11 @@ \section{Vector, Matrix and Array Constructors}\doublelabel{vector-matrix-and-ar
 \item
   \lstinline!{A, B, C, ...}! is a shorthand notation for \lstinline!array(A, B, C, ...)!.
 \item
-  There must be at least one argument {[}\emph{i.e.,} \lstinline!array()! \emph{or}
-  \lstinline!{}! \emph{is not defined}{]}.
+  There must be at least one argument.
+  \begin{nonnormative}
+  The reason \lstinline!array()! or \lstinline!{}! is not defined is that at least one argument is
+  needed to determine the type of the resulting array.
+  \end{nonnormative}
 \end{itemize}
 
 \begin{example}