- fixes possible crash when GDB connection is closed while target is running...

- fixes possible crash when GDB connection is closed while target is running due to log callback sending messages to connection which does not 
exist anymore (thanks to Pavel Chromy for this patch)


git-svn-id: svn://svn.berlios.de/openocd/trunk@325 b42882b7-edfa-0310-969c-e2dbd0fdcd60