ExtractP(\ZeroP) should be 0, and ExtractP^\bot(\bot) should be \bot.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>

protocol/protocol.tex

@@ -10721,7 +10721,7 @@ Define $\ExtractP \typecolon \GroupP \rightarrow \GroupPx$ such that
 
 \vspace{-1ex}
 \begin{formulae}
-  \item $\ExtractP\big(\ZeroP\big) = \bot$
+  \item $\ExtractP\big(\ZeroP\big) = 0$
   \item $\ExtractP\big((x, y)\big) = x \bmod \ParamP{q}$.
 \end{formulae}
 
@@ -10730,7 +10730,7 @@ We also define $\ExtractPbot \typecolon \maybe{\GroupP} \rightarrow \maybe{\Grou
 
 \vspace{-1ex}
 \begin{formulae}
-  \item $\ExtractPbot\big(\bot\big) = 0$
+  \item $\ExtractPbot\big(\bot\big) = \bot$
   \item $\ExtractPbot\big(P \typecolon \GroupP\big) = \ExtractP(P)$.
 \end{formulae}
 
@@ -14217,6 +14217,10 @@ Peter Newell's illustration of the Jubjub bird, from \cite{Carroll1902}.
 
 \historyentry{2021.1.23}{}
 \begin{itemize}
+\nufive{
+    \item Correct errors in the definitions of $\ExtractP$ and $\ExtractPbot$ in \crossref{concreteextractorpallas}:
+          $\ExtractP(\ZeroP)$ should be $0$, and $\ExtractPbot(\bot)$ should be $\bot$.
+}
     \item Fix some URLs in references.
 \end{itemize}