patch 8.2.1674: Vim9: internal error when using variable that was not set

Problem:    Vim9: internal error when using variable that was not set.
Solution:   Give a meaningful error. (closes #6937)
diff --git a/src/version.c b/src/version.c
index f30daf8..503c6ea 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1674,
+/**/
     1673,
 /**/
     1672,