Steps to reproduce the issue

Articles - Options: select 'Link to Author's Contact Page'.
Do not set the author as a contact.
View articles of the author from the front end.

Expected result

No PHP notices.

Actual result

Notice: Trying to get property 'contactid' of non-object in C:\www\joomla4\plugins\content\contact\contact.php on line 73
Notice: Trying to get property 'webpage' of non-object in C:\www\joomla4\plugins\content\contact\contact.php on line 74
Notice: Trying to get property 'email_to' of non-object in C:\www\joomla4\plugins\content\contact\contact.php on line 75

System information (as much as possible)

Wampserver 3.2.2 PHP 7.4.5 Beta2-dev Nightly Build of 9 June

Additional comments