patch 8.2.1373: Vim9: no error for assigning to non-existing script var

Problem:    Vim9: no error for assigning to non-existing script var.
Solution:   Check that in Vim9 script the variable was defined. (closes #6630)
diff --git a/src/version.c b/src/version.c
index 1e23a08..7b1b8d8 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1373,
+/**/
     1372,
 /**/
     1371,