Add check for fd < 0 in perf_reader_free

Signed-off-by: Brenden Blanco <[email protected]>

src/cc/perf_reader.c

@@ -54,7 +54,8 @@ void perf_reader_free(void *ptr) {
  if (ptr) {
  struct perf_reader *reader = ptr;
  munmap(reader->base, reader->page_size * (reader->page_cnt + 1));
- close(reader->fd);
+ if (reader->fd >= 0)
+ close(reader->fd);
  free(reader->buf);
  free(ptr);
  }