patch 9.1.1023: Coverity complains about dereferencing NULL pointer

Problem:  Coverity complains about dereferencing NULL pointer
Solution: Verify curdiff is not null before dereferencing it

closes: #16437

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index f2d7756..92bba85 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1023,
+/**/
     1022,
 /**/
     1021,