LdapConnnection: Don't pass param `$serverCtrls` to `ldap_search` prior php 7.3

refs #4013

library/Icinga/Protocol/Ldap/LdapConnection.php

@@ -1294,7 +1294,6 @@ class LdapConnection implements Selectable, Inspectable
                 throw new LogicException('LDAP scope %s not supported by ldapSearch', $scope);
         }
 
-        $serverctrls = [];
         if ($pageSize !== null) {
             $serverctrls[] = [
                 'oid' => LDAP_CONTROL_PAGEDRESULTS,
@@ -1306,7 +1305,6 @@ class LdapConnection implements Selectable, Inspectable
                     'cookie' => ''
                 ]
             ];
-        }
 
             return @$function(
                 $this->getConnection(),
@@ -1319,6 +1317,18 @@ class LdapConnection implements Selectable, Inspectable
                 $deref,
                 $serverctrls
             );
+        } else {
+            return @$function(
+                $this->getConnection(),
+                $baseDn,
+                $queryString,
+                $attributes,
+                $attrsonly,
+                $sizelimit,
+                $timelimit,
+                $deref
+            );
+        }
     }
 
     /**