kcms/lookandfeel: Guard for QGuiApplication before using styles
LookandFeelManager is invoked from QCoreApplcation startplasma. This must remain a QCoreApplication as it starts up kwin_wayland.
This newly added safety check in lookandfeelmanager meant we loaded the style. Use of QGui libraries in a QCoreApplication is undefined or worse.
startplasma should only call us with a hardcoded default.
Edited by David Edmundson