static ServiceTracker object crashes in ServiceTracker::Close()

[jeffdiclemente]

Maintaining a static ServiceTracker object can cause the program to crash on termination in ServiceTracker::Close().

The seg fault is caused by accessing the a nullptr CoreBundleContext pointer in BundleContext::GetLogSink()

test case:

#include "cppmicroservices/Framework.h"
#include "cppmicroservices/FrameworkEvent.h"
#include "cppmicroservices/FrameworkFactory.h"
#include <cppmicroservices/ServiceInterface.h>
#include "cppmicroservices/ServiceTracker.h"

#include <memory>

// A dummy interface to use with the service tracker
namespace {
    class Foo {
    public:
        virtual ~Foo() = default;
    };
}
CPPMICROSERVICES_DECLARE_SERVICE_INTERFACE(Foo, "org.cppmicroservices.test.servicetracker.Foo");

int main()
{
    auto f = cppmicroservices::FrameworkFactory().NewFramework();
    ASSERT_TRUE(f);
    f.Start();

    static std::shared_ptr<cppmicroservices::ServiceTracker<Foo>> globalTracker(std::make_shared<cppmicroservices::ServiceTracker<Foo>>(f.GetBundleContext()));
    globalTracker->Open();

    f.Stop();
    f.WaitForStop(std::chrono::milliseconds::zero());
}
// seg fault access violation when this process destroys static objects...

Minimally ServiceTracker::Close() shouldn't crash if the Framework has been destroyed.