patch 8.2.1691: Vim9: list<any> is not accepted where list<number> is expected

Problem:    Vim9: list<any> is not accepted where list<number> is expected.
Solution:   Add functions to allocate and free a type_T, use it in
            ISN_CHECKTYPE. (closes #6959)
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 533f5b9..f96a4c4 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -386,11 +386,14 @@
     static type_T *
 ret_remove(int argcount UNUSED, type_T **argtypes)
 {
-    if (argtypes[0]->tt_type == VAR_LIST
-	    || argtypes[0]->tt_type == VAR_DICT)
-	return argtypes[0]->tt_member;
-    if (argtypes[0]->tt_type == VAR_BLOB)
-	return &t_number;
+    if (argtypes != NULL)
+    {
+	if (argtypes[0]->tt_type == VAR_LIST
+		|| argtypes[0]->tt_type == VAR_DICT)
+	    return argtypes[0]->tt_member;
+	if (argtypes[0]->tt_type == VAR_BLOB)
+	    return &t_number;
+    }
     return &t_any;
 }
 
@@ -2915,7 +2918,7 @@
 {
     if (argcount == 1 && argtypes[0]->tt_type == VAR_STRING)
 	return &t_func_any;
-    return &t_func_void;
+    return &t_func_unknown;
 }
 
 /*