IoUringAssmEngn: destroy prev cb obj

This should ensure that the sh_ptr<contin> from the prev object
gets destroyed properly.

stimBuffApis/livoxGen1/ioUringAssemblyEngine.cpp

@@ -286,6 +286,7 @@ void IoUringAssemblyEngine::stop(bool doAcquireLock)
 
 	// Cancel in-flight stall timeout timer
 	stallTimer.cancel();
+	onCqeReadyCallback = std::move([](void *, int){});
 
 	if (isSetup)
 	{