Fix null pointer dereference.

In the function dump_thread_info, if /proc/<PID>/comm is unreadable, then
threadname will be used in a strncmp causing a crash. The fix is to
avoid the check if threadname is null.

Bug: 28615417
Change-Id: I54eda86404c927dbf5a987f5dd2108487df9f16c
1 file changed