patch 8.2.2028: Coverity warns for using an uninitialized variable

Problem:    Coverity warns for using an uninitialized variable.
Solution:   Initialize to NULL.
diff --git a/src/version.c b/src/version.c
index 95a0f8c..0583f64 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2028,
+/**/
     2027,
 /**/
     2026,