Don't try freeing the context in ReleaseThreadCtx
Unfortunately on certain systems, the TLS callback is called in a restricted
context, and isn't allowed to access certain messaging sub-systems. Such sub-
systems may be used if the thread's context is freed, in turn freeing the
device, which it tries to close.
Ideally, the app shouldn't have tried to destroy a context while it was still
current on a thread, or even leave a context current on a thread that's being
destroyed,. So for now, release the context ref and print an ERR that it might
be leaked.