From 1df7188596d8d68b55847f4bdc8163771440c358 Mon Sep 17 00:00:00 2001
From: gusbrs <19410606+gusbrs@users.noreply.github.com>
Date: Thu, 28 Nov 2024 15:27:29 -0300
Subject: [PATCH] Check existence of \caption@subtypehook before adding to it

---
 zref-clever.dtx | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/zref-clever.dtx b/zref-clever.dtx
index 43b3a46..1ea312a 100644
--- a/zref-clever.dtx
+++ b/zref-clever.dtx
@@ -8359,8 +8359,11 @@
 %    \begin{macrocode}
         \zref@newprop { subref }
           { \cs_if_exist_use:c { thesub \@captype } }
-        \tl_put_right:Nn \caption@subtypehook
-          { \zref@localaddprop \ZREF@mainlist { subref } }
+        \tl_if_exist:NT \caption@subtypehook
+          {
+            \tl_put_right:Nn \caption@subtypehook
+              { \zref@localaddprop \ZREF@mainlist { subref } }
+          }
       }
   }
 %    \end{macrocode}