trace-input: Init kbuf back to NULL after free kbuf
trace-input: Init kbuf back to NULL after free kbuf

Reads a wrong trace.dat file, the read_cpu_data() function returns a
failure, it will cause memory double free. we should init kbuf back to
NULL after free kbuf.

Signed-off-by: Ditang Chen <b7f0430c5977dc34733bd7ae1bc713e8d490e8e6@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <43232e92d70cc7aa53504ad0397085ee47bad87f@goodmis.org>

bigzz/trace-cmd,bigzz/trace-cmd