Eliminate warning: len may be used uninitialized

Warning issued by gcc 4.8.2 because build_logo()
returns NULL without setting the length parameter.

console.c: In function 'connect_client':
console.c:1845:26: warning: 'len' may be used uninitialized in this function [-Wmaybe-uninitialized]
         rc = send_packet (csock, (BYTE *)logoout, len, "CONNECTION RESPONSE");
                          ^
Eliminate warning: argument might be clobbered by longjmp

Warning issued by gcc 4.8.2
hscmisc.c: In function 'z900_virt_to_abs':
hscmisc.c:706:41: warning: argument 'arn' might be clobbered by 'longjmp' or 'vfork' [-Wclobbered]
                         VADR vaddr, int arn, REGS *regs, int acctype)
                                         ^