Prerequisites

• I have searched for duplicate or closed issues
• I can recreate the issue with all plugins disabled

Describe the issue

PHP version 8.4.18
After i update my roundcube from 1.6.13 to 1.7 RC4 i cant read some emails.
When i want read email i have error:

Oops... something went wrong!

An internal error has occurred. Your request cannot be processed at this time.

in logs i have this errors:

`

[27-Feb-2026 13:28:40 Europe/Warsaw] PHP Fatal error: Uncaught TypeError: array_keys(): Argument #1 ($array) must be of type array, null given in /public_html/program/lib/Roundcube/rcube_message.php:596
Stack trace:
#0 /public_html/program/lib/Roundcube/rcube_message.php(596): array_keys()
#1 /public_html/program/lib/Roundcube/rcube_message.php(617): rcube_message->parse_html_for_replacement_references()
#2 /public_html/program/lib/Roundcube/rcube_message.php(637): rcube_message->get_replacement_references()
#3 /public_html/program/actions/mail/show.php(207): rcube_message->is_referred_attachment()
#4 /public_html/program/include/rcmail_output_html.php(1498): rcmail_action_mail_show::message_attachments()
#5 [internal function]: rcmail_output_html->xml_command()
#6 /public_html/program/include/rcmail_output_html.php(1342): preg_replace_callback()
#7 /public_html/program/include/rcmail_output_html.php(815): rcmail_output_html->parse_xml()
#8 /public_html/program/include/rcmail_output_html.php(649): rcmail_output_html->parse()
#9 /public_html/program/actions/mail/show.php(163): rcmail_output_html->send()
#10 /public_html/program/include/rcmail.php(280): rcmail_action_mail_show->run()
#11 /public_html/public_html/index.php(265): rcmail->action_handler()
#12 {main}
thrown in /public_html/program/lib/Roundcube/rcube_message.php on line 596
[27-Feb-2026 13:28:42 Europe/Warsaw] PHP Warning: Undefined property: rcube_message_part::$structure in /public_html/program/lib/Roundcube/rcube_imap_cache.php on line 1209
[27-Feb-2026 13:28:42 Europe/Warsaw] PHP Warning: Undefined property: rcube_message_part::$structure in /public_html/program/lib/Roundcube/rcube_imap_cache.php on line 1209

`

What browser(s) are you seeing the problem on?

Firefox 148 and Edge

What version of PHP are you using?

8.4.18

What version of Roundcube are you using?

1.7 RC4

JavaScript errors

No response

PHP errors

No response