patch 8.2.0322: Vim9: error checks not tested

Problem:    Vim9: error checks not tested.
Solution:   Add more test cases.  Avoid error for function loaded later.
diff --git a/src/evalvars.c b/src/evalvars.c
index 894ee28..227253e 100644
--- a/src/evalvars.c
+++ b/src/evalvars.c
@@ -2541,8 +2541,10 @@
 	return &curtab->tp_vars->dv_hashtab;
     if (*name == 'v')				// v: variable
 	return &vimvarht;
-    if (current_sctx.sc_version != SCRIPT_VERSION_VIM9)
+    if (get_current_funccal() != NULL
+			      && get_current_funccal()->func->uf_dfunc_idx < 0)
     {
+	// a: and l: are only used in functions defined with ":function"
 	if (*name == 'a')			// a: function argument
 	    return get_funccal_args_ht();
 	if (*name == 'l')			// l: local function variable