Fix event deletion for kqueue

It seems that agnostic 'wide' deletion of both read and write events from kqueue
does not actually delete any of them, but fails because another doesn't exist in the time.
Later on execution it usually causes crash of the daemon.

src/searchdha.cpp

@@ -4224,10 +4224,11 @@ class KqueueEvents_c : public ISphNetPoller, public EventsList_t, public Timeout
 
 		sphLogDebugv ( "%p kqueue remove, ev=0x%u, sock=%d",
 				pEvent->m_tBack.pPtr, pEvent->m_uNetEvents, pEvent->m_iSock );
-		struct kevent tEv[2];
-		EV_SET( &tEv[0], pEvent->m_iSock, EVFILT_WRITE, EV_DELETE | EV_CLEAR, 0, 0, nullptr );
-		EV_SET( &tEv[1], pEvent->m_iSock, EVFILT_READ, EV_DELETE | EV_CLEAR, 0, 0, nullptr );
-		int iRes = kevent ( m_iKQ, tEv, 2, nullptr, 0, nullptr );
+		struct kevent tEv;
+		EV_SET( &tEv, pEvent->m_iSock,
+			( ( pEvent->m_uNetEvents & NetPollEvent_t::READ ) ? EVFILT_READ : EVFILT_WRITE ),
+			EV_DELETE | EV_CLEAR, 0, 0, nullptr );
+		int iRes = kevent ( m_iKQ, &tEv, 1, nullptr, 0, nullptr );
 
 		// might be already closed by worker from thread pool
 		if ( iRes==-1 )