Fix whitespace

chapters/operatorsandexpressions.tex

@@ -1161,7 +1161,7 @@ \subsection{Event-Related Operators with Function Syntax}\doublelabel{event-rela
 \lstinline!pre(y)! & Returns the \emph{left limit} $y(t^{-})$ of
 variable $y(t)$ at a time instant $t$. At an event instant,
 $y(t^{-})$ is the value of y after the last event
-iteration at time instant $t$ (see comment below). 
+iteration at time instant $t$ (see comment below).
 Any subscripts in the component expression $y$ must be parameter expressions.
 The \lstinline!pre()! operator can
 be applied if the following three conditions are fulfilled