"Send this topic" fail, invalid character

[a10]

An Error Has Occurred!
Invalid character used in email.

(Definitely no invalid character, only @ and normal (uk english) characters ...or... is it something in the content of the topic that kills it ??)

Log:

https://www.*******/forum/index.php?action=emailuser;sa=sendtopic;topic=11827.0
8: Undefined index: ryemail
File: /customers/*/*/*/*******/httpd.www/forum/Sources/SendTopic.php
Line: 130

Not often this is used, so zero idea when it may have started, or occured before php7\2.0.14\ssl

[Shambles]

https://www.simplemachines.org/community/index.php?topic=553943.msg3926466#msg3926466

[a10]

Thanks for info (should have found it). Fixed in 2.0.15 ?

[Illori]

should be.