Fix conditional check for allocation failure

function benc_decode was checking for strlen(in) < 1 and was using
errno to get the error message. This should be instead checking (struct
benc*) b is NULL instead.

The original condition was leaking memory as per the report by
scan-build tool.

Signed-off-by: Vasudev Kamath <kamathvasudev@gmail.com>
Fix memory leak in main function

slurp call returns allocated memory which was not freed as reported by
scan-build tool.

Signed-off-by: Vasudev Kamath <kamathvasudev@gmail.com>