ucli: fixed minor segfault with help function
ucli: fixed minor segfault with help function

If command's help was NULL (e.g., with BRCM's debug), <tab,tab>
would cause an instant segfault.

jnealtowns/bigcode,rizard/bigcode,jnealtowns/bigcode,rizard/bigcode,rizard/bigcode,rizard/bigcode,jnealtowns/bigcode,jnealtowns/bigcode,rizard/bigcode,jnealtowns/bigcode