Resolve unlink() error

[cjholowatyj]

What does it do?

Wrapped the unlink($file) call in an if statement to confirm that $file still exists.

Why is it needed?

Resolves unlink() errors that occur when concurrent requests for a cache file results in one unlink() call being successful while other unlink() calls result in a PHP error being thrown.

Related issue(s)/PR(s)

None to my knowledge