patch 9.0.1801: Vim9 instanceof() fails in a def func

Problem:  Vim9 instanceof() fails in a def func
Solution: allow Objects in compile time check

closes: #12907

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>
diff --git a/src/evalfunc.c b/src/evalfunc.c
index bdfd632..2cd1985 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -282,7 +282,11 @@
     static int
 arg_object(type_T *type, type_T *decl_type UNUSED, argcontext_T *context)
 {
-    return check_arg_type(&t_object, type, context);
+    if (type->tt_type == VAR_OBJECT
+	    || type_any_or_unknown(type))
+	return OK;
+    arg_type_mismatch(&t_object, type, context->arg_idx + 1);
+    return FAIL;
 }
 
 /*