patch 8.0.1500: possible NULL pointer dereference

Problem:    Possible NULL pointer dereference. (Coverity)
Solution:   Check for the pointer not being NULL.
diff --git a/src/version.c b/src/version.c
index a7cc0e4..4cbfc47 100644
--- a/src/version.c
+++ b/src/version.c
@@ -772,6 +772,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1500,
+/**/
     1499,
 /**/
     1498,