patch 8.2.3650: Vim9: for loop variable can be a list member

Problem:    Vim9: for loop variable can be a list member.
Solution:   Check for valid variable name. (closes #9179)
diff --git a/src/dict.c b/src/dict.c
index aa3c611..032c1b5 100644
--- a/src/dict.c
+++ b/src/dict.c
@@ -1102,7 +1102,7 @@
 			&& HI2DI(hi2)->di_tv.v_type == VAR_FUNC
 			&& var_wrong_func_name(hi2->hi_key, di1 == NULL))
 		    break;
-		if (!valid_varname(hi2->hi_key, TRUE))
+		if (!valid_varname(hi2->hi_key, -1, TRUE))
 		    break;
 	    }