The following example cause crash instead of failures
err = jvmti->GetFrameLocation(thr, 0, &mid, &loc);
    if (err != JVMTI_ERROR_NONE) {
        printf("(GetFrameLocation) unexpected error: %s (%d)\n",
               TranslateError(err), err);
        result = STATUS_FAILED;
    }

The "mid" and "loc" shouldn't be used if GetFrameLocation failed.
Immediate return from the function is needed if it failed with non-JVMTI_ERROR_NONE.