patch 8.2.0973: Vim9: type is not checked when assigning to a script variable

Problem:    Vim9: type is not checked when assigning to a script variable.
Solution:   Check the type.
diff --git a/src/version.c b/src/version.c
index 2996d3b..d2f442c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    973,
+/**/
     972,
 /**/
     971,