8c35190b0 moved the Servers lookup into a foreach over $s but kept
define('ZM_SERVER_ID', $Server->Id()), so every request on a node with
ZM_SERVER_NAME in zm.conf died with 'Call to a member function Id() on
null'. Use $s like the ZM_SERVER_HOST branch.
Also make the 'no corresponding entry in Servers table' errors reachable
($thisServer starts as an empty Server object, which is always truthy,
so test its Id) and concatenate the ZM_SERVER_ID error with '.' instead
of '+', which throws a TypeError on PHP 8.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>