Free value if dup succeed but listAddNodeTail failed. (#8901)

This fix is in dead code.
see redisOutOfMemoryHandler an allocation can't fail.
but maybe someone will copy this code to a different project
some day, better have this fixed

Co-authored-by: Oran Agra <oran@redislabs.com>

src/adlist.c

@@ -269,9 +269,14 @@ list *listDup(list *orig)
                 listRelease(copy);
                 return NULL;
             }
-        } else
+        } else {
             value = node->value;
+        }
+        
         if (listAddNodeTail(copy, value) == NULL) {
+            /* Free value if dup succeed but listAddNodeTail failed. */
+            if (copy->free) copy->free(value);
+
             listRelease(copy);
             return NULL;
         }