Initialise a non-statically-allocated WeakRef.
This function also calls @set with object on the freshly-initialised
weak reference.
This function should always be matched with a call to g_weak_ref_clear. It is not necessary to use this function for a
WeakRef in static storage because it will already be properly initialised. Just use
@set directly.
| this |
uninitialized or empty location for a weak reference |
| object |
a Object or null |