FIXED: #1414 crash in C_CUT due to reset clause pointer from undo/1.

Author: JanWielemaker

src/pl-vmi.c

@@ -6629,7 +6629,6 @@ VMH(deep_backtrack, 1, (int), (trace_action))
     { bool rc;
 
       lTop = (LocalFrame)(BFR+1);
-      FR->clause = NULL;
       if ( LD->mark_bar != NO_MARK_BAR )
 	LD->mark_bar = gTop;
       SAVE_REGISTERS(QID);

tests/core/test_undo.pl

@@ -2,10 +2,11 @@
 
     Author:        Jan Wielemaker
     E-mail:        [email protected]
-    WWW:           http://www.swi-prolog.org
-    Copyright (c)  2021, University of Amsterdam
-                         VU University Amsterdam
-		         CWI, Amsterdam
+    WWW:           https://www.swi-prolog.org
+    Copyright (c)  2021-2025, University of Amsterdam
+                              VU University Amsterdam
+		              CWI, Amsterdam
+                              SWI-Prolog Solutions b.v.
     All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
@@ -67,6 +68,8 @@
           x,
           true),
     \+ a(3).
+test(cleanup, fail) :-                 % issue #1414
+    \+ \+ once((undo(true), fail)).
 
 ok.