Fix Undefined array key "afi" in bgp.inc.php (librenms#18083)

We need to make sure we wrap the ternary check in parentheses so it can do the evaluation rather than executing `$peer['afi']` first - leading to a php error

Author: zappiehost

includes/html/pages/routing/bgp.inc.php

@@ -325,7 +325,7 @@
             <td width=30><b>&#187;</b></td>
             <td width=150>' . $peeraddresslink . '<br />' . Url::deviceLink($peer_device, vars: ['tab' => 'routing', 'proto' => 'bgp']) . "</td>
             <td width=50><b>$peer_type</b></td>
-            <td width=50>" . $peer['afi'] ?? '' . '</td>
+            <td width=50>" . ($peer['afi'] ?? '') . '</td>
             <td><strong>AS' . $peer['bgpPeerRemoteAs'] . '</strong><br />' . $peer['astext'] . '</td>
             <td>' . $peer['bgpPeerDescr'] . "</td>
             <td><strong><span style='color: $admin_col;'>" . $peer['bgpPeerAdminStatus'] . "</span><br /><span style='color: $col;'>" . $peer['bgpPeerState'] . '</span></strong></td>