Gets back user data pointers stored via set_qdata and removes the data
from this without invoking its destroy function (if any was set).
Usually, calling this function is only required to update user data pointers with a destroy notifier.
| this |
the ParamSpec to get a stored user data pointer from |
| quark |
a Quark, naming the user data pointer |
|
the user data pointer set, or null |