imapc: Update mail size also when istream_opened() hook is called

When fetching a message body the cached message size was set. However,
if istream_opened() hook was used this wasn't done. If a client had
fetched both (RFC822.SIZE BODY.PEEK[]) and the server sent a wrong
RFC822.SIZE, that size was used for the message body size, which resulted
in "Cached message size larger than expected" errors.

src/lib-storage/index/imapc/imapc-mail-fetch.c

@@ -576,7 +576,8 @@ void imapc_mail_init_stream(struct imapc_mail *mail)
 			index_mail_close_streams(imail);
 			return;
 		}
-	} else if (mail->body_fetched) {
+	}
+	if (mail->body_fetched) {
 		ret = i_stream_get_size(imail->data.stream, TRUE, &size);
 		if (ret < 0) {
 			index_mail_close_streams(imail);