Memcache Admin - Some of the statistics not shown correctly due to null coalescing operator misinterpretation

Problem/Motivation

Noticed that some of the statistics are not shown correctly in Memcache Statistics page, e.g.
- Gets
- Transferred
- Per-connection average

Reason for that seems to be slight misinterpretation of syntax when stats lines in code using ternary operator were changed to use new null coalescing operator (PHP7), i.e.

$hits = isset($this->stats['get_hits']) ? $this->stats['get_hits'] : 0;
was changed to
$hits = isset($this->stats['get_hits']) ?? 0;
which will result either 1 or 0.

Intended / correct change would be:
$hits = $this->stats['get_hits'] ?? 0;

that is identical to this if/else statement

if (isset($this->stats['get_hits'])) {
  $hits = $this->stats['get_hits'];
} else {
  $hits = 0;
}

Steps to reproduce

- Install memcache
- Install memcache_admin
- Visit in Memcache Statistics page

Proposed resolution

Fix stats lines syntax having null coalescing operator