Do not throw an exception when passing bogus parameters to hovercards but properly handle the missing array index by setting $object_phid to null.
In consequence, see a proper hovercard correctly displaying Unknown Object (????) instead of an exception.
Closes T15969
Thanks! P.S. I see that Phorge also usually do a short-circuit
Maybe useful also for less indentations, easier git blame
(not a blocking comment - just tip)