Icons of source files in qtcreator tree widget disappeared

[laine]

I don't know what have I done that the icons of source files (*.h and *.cpp) disappeared in project tree-widget, just as the picture shown.

I use cmake to manager my project. The problems appears today, and qtcreator works good before.

Platform Windows 10.
QtCreator 4.9.0

What should I do to recover qtcreator ?