patch 9.1.0688: Vim9: dereferences NULL pointer in check_type_is_value()

Problem:  Vim9: dereferences NULL pointer in check_type_is_value()
          (Suyue Guo)
Solution: Verify that the pointer is not Null

fixes: #15540
closes: #15545

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index 72cce65..e77ef0f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    688,
+/**/
     687,
 /**/
     686,