Function block_on_jni 

pub fn block_on_jni<T: Send + 'static>(
    env: &mut JNIEnv<'_>,
    _context: &str,
    fut: impl Future<Output = T> + Send + 'static,
) -> Option<T>

Block on a future from a JNI entry point, panic-safe.

• If a Tokio runtime is already active on this thread, fut is polled to completion inside that runtime (spawn + block_on the JoinHandle).
• Otherwise the future runs on the process-wide JNI runtime.
• Any panic inside fut is caught and re-thrown to Java as a com.dunimd.ri.RiError instead of aborting the JVM.

Returns None when a panic was caught (a Java exception is pending).