zlib: zlib_mailbox_open_input() can't fail - remove dead code

src/plugins/zlib/zlib-plugin.c

@@ -253,7 +253,7 @@ zlib_permail_alloc_init(struct mailbox *box, struct mailbox_vfuncs *v)
 	}
 }
 
-static int zlib_mailbox_open_input(struct mailbox *box)
+static void zlib_mailbox_open_input(struct mailbox *box)
 {
 	const struct compression_handler *handler;
 	struct istream *input;
@@ -262,7 +262,7 @@ static int zlib_mailbox_open_input(struct mailbox *box)
 
 	handler = compression_lookup_handler_from_ext(box->name);
 	if (handler == NULL || handler->create_istream == NULL)
-		return 0;
+		return;
 
 	if (mail_storage_is_mailbox_file(box->storage)) {
 		/* looks like a compressed single file mailbox. we should be
@@ -273,19 +273,18 @@ static int zlib_mailbox_open_input(struct mailbox *box)
 		if (fd == -1) {
 			/* let the standard handler figure out what to do
 			   with the failure */
-			return 0;
+			return;
 		}
 		if (fstat(fd, &st) == 0 && S_ISDIR(st.st_mode)) {
 			i_close_fd(&fd);
-			return 0;
+			return;
 		}
 		input = i_stream_create_fd_autoclose(&fd, MAX_INBUF_SIZE);
 		i_stream_set_name(input, box_path);
 		box->input = handler->create_istream(input, TRUE);
 		i_stream_unref(&input);
 		box->flags |= MAILBOX_FLAG_READONLY;
 	}
-	return 0;
 }
 
 static int zlib_mailbox_open(struct mailbox *box)
@@ -294,10 +293,8 @@ static int zlib_mailbox_open(struct mailbox *box)
 
 	if (box->input == NULL &&
 	    (box->storage->class_flags &
-	     MAIL_STORAGE_CLASS_FLAG_OPEN_STREAMS) != 0) {
-		if (zlib_mailbox_open_input(box) < 0)
-			return -1;
-	}
+	     MAIL_STORAGE_CLASS_FLAG_OPEN_STREAMS) != 0)
+		zlib_mailbox_open_input(box);
 
 	return zbox->super.open(box);
 }