[LAD] jack_midi in jackd and jackdmp

Hi to all Thats my first post to the dev list, first I wont to say hello, and sorry for my bad english. I try to do my best to make it readable for you. So,. . I try to build a jack_midi output port and I get the stuff working with jackd(1). But my test's with jackdmp end up with crash's (segfaults). I realise that's because the needed buffer recived from jack_port_get_buffer(midi_output_ports, nframes) is == 0 when I run jackdmp-1.9.2. jackd gives me a buffer from 480. I 'am only be able to protect the port for crash's but I can't figure out what I make wrong. I try and I try and I try, but I can't get now . . . It would be realy great if someone from the list here is willing to have a lock at my source and give me a hint to drive me in the right direction. My (uggly) sources are here : http://apps.sourceforge.net/trac/guitarix/browser/trunk/src/main.cpp midi_process callback start's at line 233 regards hermann