patch 8.2.2131: Vim9: crash when lambda uses same var as assignment

Problem:    Vim9: crash when lambda uses same var as assignment.
Solution:   Do not let lookup_local change lv_from_outer, make a copy.
            (closes #7461)
diff --git a/src/proto/evalvars.pro b/src/proto/evalvars.pro
index 39ea338..0449ea5 100644
--- a/src/proto/evalvars.pro
+++ b/src/proto/evalvars.pro
@@ -59,7 +59,7 @@
 dictitem_T *find_var(char_u *name, hashtab_T **htp, int no_autoload);
 dictitem_T *find_var_in_ht(hashtab_T *ht, int htname, char_u *varname, int no_autoload);
 hashtab_T *get_script_local_ht(void);
-void *lookup_scriptvar(char_u *name, size_t len, cctx_T *dummy);
+int lookup_scriptvar(char_u *name, size_t len, void *lvar, cctx_T *dummy);
 hashtab_T *find_var_ht(char_u *name, char_u **varname);
 char_u *get_var_value(char_u *name);
 void new_script_vars(scid_T id);