This page should help developers to find solutions for known problems.
Remove the build directories of all applications built by yourself (like Kaidan itself, QXmpp, Kirigami etc.) and build them again.
Remove all QXmpp related files which were installed on your system by make install:
sudo rm -r $(find /usr/local -name "*qxmpp*")
After that you may install QXmpp again via make install.