segfault in libjack from incorrect regex in jack_get_ports()

[7890]

Check return value from regcomp() to handle invalid regular expressions.

https://github.com/jackaudio/jack1/blob/master/libjack/client.c#L3019
https://github.com/jackaudio/jack1/blob/master/libjack/client.c#L3023

See jackaudio/jack2#433