core: Fix reference count leak for default context
core: Fix reference count leak for default context

If the default context was created but failed to fully initialize,
the reference count was not decremented appropriately.

dickens/libusb,tklauser/libusb,bra1nb3am3r/libusb,YesVideo/libusb,ButterflyNetwork/libusb,BuLogics/libusb,weizhenwei/libusb,LudovicRousseau/libusb,JENETRIC/libusb,weizhenwei/libusb,wuzhenda/libusb,tonyarkles/libusb,HounD/libusb-v1.0.19,philemonf/libusb,libusb/libusb,tklauser/libusb,daiguangbao/libusb,andyvand/libusb,YesVideo/libusb,jwrdegoede/libusbx,tonyarkles/libusb,LudovicRousseau/libusb,erhuabushuo/libusb,jwrdegoede/libusbx,dmitrykos/libusb,erhuabushuo/libusb,kuldeepdhaka/libusb,AmesianX/libusb,LudovicRousseau/libusb,dmitrykos/libusb,kuldeepdhaka/libusb,SimplyComplexCo/libusb,SimplyComplexCo/libusb,AmesianX/libusb,BuLogics/libusb,wuzhenda/libusb,daiguangbao/libusb,YesVideo/libusb,kuldeepdhaka/libusb,libusb/libusb,dickens/libusb,philemonf/libusb,tonyarkles/libusb,philemonf/libusb,SimplyComplexCo/libusb,philemonf/libusb,BuLogics/libusb,ButterflyNetwork/libusb,daiguangbao/libusb,ButterflyNetwork/libusb,bra1nb3am3r/libusb,JENETRIC/libusb,dickens/libusb,AmesianX/libusb,leapmotion/libusb,anilgit90/libusb,ButterflyNetwork/libusb,HounD/libusb-v1.0.19,bra1nb3am3r/libusb,libusb/libusb,leapmotion/libusb,weizhenwei/libusb,dmitrykos/libusb,jwrdegoede/libusbx,anilgit90/libusb,andyvand/libusb,wuzhenda/libusb,andyvand/libusb,anilgit90/libusb,JENETRIC/libusb,HounD/libusb-v1.0.19,erhuabushuo/libusb,tklauser/libusb,leapmotion/libusb,ButterflyNetwork/libusb,dmitrykos/libusb