perf evlist: Avoid iteration for empty evlist.

As seen with 'perf stat --null ..' and reported in:
https://lore.kernel.org/lkml/[email protected]/

v2. Avoids setting evsel in the empty list case as suggested by Jiri Olsa.

    Committer testing:

Before:

  $  perf stat --null sleep 1
  Segmentation fault (core dumped)
  $

After:

  $  perf stat --null sleep 1

   Performance counter stats for 'sleep 1':

         1.010340646 seconds time elapsed

         0.001420000 seconds user
         0.000000000 seconds sys
  $

Fixes: 472832d2c000b961 ("perf evlist: Refactor evlist__for_each_cpu()")
Reported-by: Arnaldo Carvalho de Melo <[email protected]>
Signed-off-by: Ian Rogers <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Acked-by: Jiri Olsa <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Namhyung Kim <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

0 files changed, 0 insertions, 0 deletions