Fixed regex incident.

src/fa/duality/polar.tex

@@ -27,7 +27,7 @@
     \begin{enumerate}
         \item $\emptyset^\circ = \emptyset^\square = F$ and $F^\circ = F^\square = \bracs{0}$. 
         \item For any $A, B \subset E$ and $\lambda \ne 0$, if $\lambda A \subset B$, then $B^\circ \subset \lambda^{-1}A^\circ$. 
-    \end\{enumerate\}
+    \end{enumerate}
 
     
 \end{proposition}