Fetch a handle type in FILE_GetUnixHandle.

diff --git a/server/serial.c b/server/serial.c
index 614be00..d6a1ea4 100644
--- a/server/serial.c
+++ b/server/serial.c
@@ -160,18 +160,20 @@
 
 static int serial_get_info( struct object *obj, struct get_file_info_request *req )
 {
-    assert( obj->ops == &serial_ops );
-    req->type        = FILE_TYPE_CHAR;
-    req->attr        = 0;
-    req->access_time = 0;
-    req->write_time  = 0;
-    req->size_high   = 0;
-    req->size_low    = 0;
-    req->links       = 0;
-    req->index_high  = 0;
-    req->index_low   = 0;
-    req->serial      = 0;
-    return 1;
+    if (req)
+    {
+        req->type        = FILE_TYPE_CHAR;
+        req->attr        = 0;
+        req->access_time = 0;
+        req->write_time  = 0;
+        req->size_high   = 0;
+        req->size_low    = 0;
+        req->links       = 0;
+        req->index_high  = 0;
+        req->index_low   = 0;
+        req->serial      = 0;
+    }
+    return FD_TYPE_DEFAULT;
 }
 
 /* these function calculates the timeout for an async operation