patch 8.1.0437: may access freed memory when syntax HL times out

Problem:    May access freed memory when syntax HL times out. (Philipp Gesang)
Solution:   Clear b_sst_first when clearing b_sst_array.
diff --git a/src/version.c b/src/version.c
index 7f21f2d..55d3d80 100644
--- a/src/version.c
+++ b/src/version.c
@@ -795,6 +795,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    437,
+/**/
     436,
 /**/
     435,