From d8ce6d2c046c2ee34e9f797eacac1ebe45d67c19 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Ke=C3=9Fler?= <git@maximilian-kessler.de>
Date: Sun, 23 Jan 2022 16:28:18 +0100
Subject: [PATCH] add missing check for existence of group when flattening
 group hierarchy

---
 doc/environments/groupthm/groupthm.dtx | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/doc/environments/groupthm/groupthm.dtx b/doc/environments/groupthm/groupthm.dtx
index f6f5207..901b215 100644
--- a/doc/environments/groupthm/groupthm.dtx
+++ b/doc/environments/groupthm/groupthm.dtx
@@ -1851,6 +1851,7 @@
       }
       {
         \seq_pop:NN \l_tmpa_seq \l_tmpa_tl
+        \@@_ensure_group_exists:V \l_tmpa_tl
         \clist_if_in:NVF #2 \l_tmpa_tl
           {
             \clist_put_left:NV #2 \l_tmpa_tl
@@ -1972,7 +1973,7 @@
 % 
 %
 %
-% \begin{macro}{\@@_ensure_group_exists:n}
+% \begin{macro}{\@@_ensure_group_exists:n, \@@_ensure_group_exists:V}
 %    \begin{syntax}
 %       \cs{@@_ensure_group_exists:n}\meta{theorem group}
 %    \end{syntax}
@@ -1988,6 +1989,7 @@
       \msg_error:nnn { groupthm } { unknown ~ group } { #1 }
     }
   }
+\cs_generate_variant:Nn \@@_ensure_group_exists:n { V }
 %    \end{macrocode}
 % \end{macro}
 %