patch 8.2.1702: crash when using undo after deleting folded lines

Problem:    Crash when using undo after deleting folded lines.
Solution:   Check for NULL pointer. (closes #6968)
diff --git a/src/version.c b/src/version.c
index e06b566..9d87cdb 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1702,
+/**/
     1701,
 /**/
     1700,