Fix empty topos

Thanks to Manuel Hoff
https://stacks.math.columbia.edu/tag/00X9#comment-4362

sites.tex

@@ -2841,14 +2841,14 @@ \section{Topoi}
 use this abuse of notation.
 
 \medskip\noindent
-Two examples of topoi. The {\it empty topos} is topos
-of sheaves on the site $\mathcal{C}$, where $\mathcal{C}$ has
-a single object $\emptyset$ and a single morphism $\text{id}_\emptyset$
-and a single covering, namely the empty covering of $\emptyset$.
-We will sometimes write $\emptyset$ for this site.
-This is a site and every sheaf on $\mathcal{C}$ assigns a singleton to
-$\emptyset$. Thus $\Sh(\emptyset)$ is equivalent to the category
+The {\it empty topos} is topos
+of sheaves on the site $\mathcal{C}$, where $\mathcal{C}$
+is the empty category. We will sometimes write $\emptyset$ for this site.
+This is a site which has a unique sheaf (since $\emptyset$ has no
+objects). Thus $\Sh(\emptyset)$ is equivalent to the category
 having a single object and a single morphism.
+
+\medskip\noindent
 The {\it punctual topos} is the topos of sheaves on the site
 $\mathcal{C}$ which has a single object $pt$ and one morphism
 $\text{id}_{pt}$ and whose only covering is the covering