Caps element with missing attributes. Attributes: hash=null version=0.95.5.13931 node=http://miranda-ng.org/caps
It looks like the user received a message from a very old Miranda client that doesn’t properly use the XMPP protocol and doesn’t set the required hash attribute for XEP-0115 Entity Capabilities.
The problem was fixed in 2017 XMPP CAPS data is missing required attribute value. · Issue #667 · miranda-ng/miranda-ng · GitHub
The second exception is more complicated. It’s hard to tell what was wrong. In the code at that place it tries to add a line to the chat text view. It only tries to get message styles so try to change ChatRoomFontSize, messageColor or backgroundColor. Maybe they weren’t set properly.
Which Java version do you use? Maybe try to upgrade it.