patch 9.1.1474: missing out-of-memory check in mark.c

Problem:  missing out-of-memory check in mark.c
Solution: bail out, if mark_line() returns NULL
          (John Marriott)

closes: #17578

Signed-off-by: John Marriott <basilisk@internode.on.net>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index bafcef1..8f9033b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -710,6 +710,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1474,
+/**/
     1473,
 /**/
     1472,