Description:
------------
When I use null coalescing operator on a class implementing ArrayAccess then offsetExists is not called, but offsetGet is called instead (which may trigger some error). It should be equivalent to ternary operator with isset.

https://3v4l.org/Xbojv

There is a similar issue with __get and __isset methods https://bugs.php.net/bug.php?id=71359

Test script:
---------------
<?php
$data = new class implements \ArrayAccess
{
	public function offsetExists($offset)
	{
		echo "offsetExists\n";
	}


	public function offsetGet($offset)
	{
		echo "offsetGet\n";
	}


	public function offsetSet($offset, $value)
	{
	}


	public function offsetUnset($offset)
	{
	}

};
echo "isset:\n";
isset($data['foo']) ? NULL : NULL;
echo "null coalescing operator:\n";
$data['foo'] ?? NULL;

Expected result:
----------------
isset:
offsetExists
null coalescing operator:
offsetExists

Actual result:
--------------
isset:
offsetExists
null coalescing operator:
offsetGet