[imp] Message content not displayed after upgrade to PHP 7.3

[Arjen de Korte]

Citeren Arjen de Korte <build+horde at de-korte.org>:

> Just a heads-up for those that what to upgrade to PHP 7.3: it seems  
> like there are some incompatibilities with Horde (master) in  
> handling regular expressions.
>
> Some (but not all) messages will not display content. The following  
> is logged for each message:
>
> 2018-12-25T12:47:27+01:00 WARN: horde [imp] PHP ERROR: preg_replace_callback(
> ): Compilation failed: invalid range in character class at offset 68 [pid 207
> 6 on line 99 of "/usr/share/php7/PEAR/Horde/Text/Filter.php"]
> 2018-12-25T12:47:27+01:00 WARN: horde [imp] PHP ERROR: preg_replace_callback(
> ): Compilation failed: invalid range in character class at offset 649 [pid 20
> 76 on line 99 of "/usr/share/php7/PEAR/Horde/Text/Filter.php"]
>
> This may be due to the stricter interpretation of character ranges  
> in classes.

Note that the message content is available. I can reply to such a  
message (like the one quoted above) just fine. So the trouble seems to  
be in rendering messages, rather than grabbing them from the IMAP  
server.