empty dialog shown

[marvin]

hi,
i'm using qt creator, i made a new project with mainwindow (mainwindow.ui, mainwindow.h, mainwindow.cpp), then added a dialog called members.ui, source (members.cpp) and header (members.h) file, but when i want to show the dialog i get an empty dialog instead
here are sources i consider relevant:
mainwindow.cpp
members.cpp
members.h
I'm new to Qt so it might be something trivial...

Thank you.

EDIT: attached files