fix compiler warning
fix compiler warning

Ilyatk/qxmpp,pol51/QXMPP-CMake,Ilyatk/qxmpp,pol51/QXMPP-CMake,LightZam/qxmpp,Kaffeine/qxmpp,kollix/qxmpp,ycsoft/qxmpp,olesalscheider/qxmpp,kollix/qxmpp,cccco/qxmpp,Kaffeine/qxmpp,gamenet/qxmpp,cccco/qxmpp,KangLin/qxmpp,olesalscheider/qxmpp,ycsoft/qxmpp,ycsoft/qxmpp,gamenet/qxmpp,cccco/qxmpp,pol51/QXMPP-CMake,Ilyatk/qxmpp,KangLin/qxmpp,LightZam/qxmpp,Kaffeine/qxmpp,olesalscheider/qxmpp,LightZam/qxmpp,gamenet/qxmpp,kollix/qxmpp,KangLin/qxmpp