In the NativeGSSContext constructor for imported context, the assert is use on the object field, instead of the input parameters. As the NativeGSSContext object does not exist yet, this looks like an obvious issue.

    NativeGSSContext(long pCtxt, GSSLibStub stub) throws GSSException {
- assert(pContext != 0);
+ assert(pCtxt != 0);
        pContext = pCtxt;
        ...