kernelshark: Fix seting of clear task menu
kernelshark: Fix seting of clear task menu

The clear_task_menu was being updated by the set_menu_label()
helper function. But that function expects a "comm" passed to it.
The clear_task_menu may be updated when comm is NULL, and this would
cause a strlen(comm) to crash the program.

Signed-off-by: Steven Rostedt <43232e92d70cc7aa53504ad0397085ee47bad87f@goodmis.org>

bigzz/trace-cmd,bigzz/trace-cmd