build: Fix another compilation error with Qt 5.3
build: Fix another compilation error with Qt 5.3

Regressed in 3d72371a5b

Refs #68352

savoirfairelinux/ring-lrc,KDE/libringclient,KDE/libringclient,KDE/libringclient,savoirfairelinux/ring-lrc,savoirfairelinux/ring-lrc,savoirfairelinux/ring-lrc,savoirfairelinux/ring-lrc