patch 8.2.2374: accessing uninitialized memory in test_undo

Problem:    Accessing uninitialized memory in test_undo.
Solution:   Do not look in typebuf.tb_buf if it is empty. (Dominique Pellé,
            closes #7697)
diff --git a/src/version.c b/src/version.c
index f1b7280..98f120b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2374,
+/**/
     2373,
 /**/
     2372,