Index is garbled in GNU Screen due to U+061C ARABIC LETTER MARK characters in the subject

I've received a spam with U+061C ARABIC LETTER MARK characters in the subject, which makes the index garbled in GNU Screen. I don't know what they are, but they should probably be filtered out. This can be tested on

From a@b.invalid Tue May 24 18:41:15 2022
Subject: =?utf-8?B?2JzYnNicyaHYnNic2JzYnNic2JzQsNic2JzYnNic2JzYnG4=?=
 =?utf-8?B?2JzYnNic2JzYnNic1IHYnNic2JzYnNic2JzRli5u2JzYnA==?=
 =?utf-8?B?2JzYnNic2JzQtdic2JzYnNic2JzYnHTYnNic2Jwg2JzYnA==?=
 =?utf-8?B?2JwgUtic2JzYnNic2JzYnNC12JzYnNic2JzYnNicbtic?=
 =?utf-8?B?2JzYnNic2JzYnNC+2JzYnNic2JzYnNicddic2JzYnNic2Jw=?=
 =?utf-8?B?2JzhtKDYnNic2JzYnNic2JzQtdic2JzYnNic2JzYnGzYnNic?=
 =?utf-8?B?2JzYnNic2Jxs2JzYnNic2JzYnNic0LXYnNic2JzYnNic2Jw=?=
 =?utf-8?B?bdic2JzYnNic2JzYnNC12JzYnNic2JzYnNicbtic2JzYnA==?=
 =?utf-8?B?2JzYnNicdNic2JzYnCB2aW5jMTcub3Jn?=
 =?utf-8?B?ICE=?=

Also attached: mscreen-202205.mbox

For instance:

screen mutt -F /dev/null -f mscreen-202205.mbox

The status line is 2 lines above the correct position.

When such a message is in a real mailbox, the index is completely garbled.

Note that even the way the subject is shown when viewing the message outside of GNU Screen looks suspicious, on 3 lines: