Avoid a class ref/unref when creating C extensions
Avoid a class ref/unref when creating C extensions

No point in doing this each time when
it can be done just once. Also verify
that the property is of the correct type.

gregier/libpeas,chergert/libpeas,GNOME/libpeas,gregier/libpeas,GNOME/libpeas,gregier/libpeas,gregier/libpeas,chergert/libpeas,chergert/libpeas