Error: undefined reference to `vtable for mydemo'

[mishra39]

I cloned the repo and ran catkin build and received the following error:
CMakeFiles/ros_cv_gui_demo_node.dir/src/mydemo.cpp.o: In function mydemo::mydemo(QWidget*)': mydemo.cpp:(.text+0x69): undefined reference to vtable for mydemo'
mydemo.cpp:(.text+0x7e): undefined reference to vtable for mydemo' CMakeFiles/ros_cv_gui_demo_node.dir/src/mydemo.cpp.o: In function mydemo::~mydemo()':
mydemo.cpp:(.text+0x779): undefined reference to vtable for mydemo' mydemo.cpp:(.text+0x78b): undefined reference to vtable for mydemo'
collect2: error: ld returned 1 exit status
make[2]: *** [/home/NEA.com/akshit.mishra/catkin_ws/devel/.private/ros_cv_gui_demo/lib/ros_cv_gui_demo/ros_cv_gui_demo_node] Error 1
make[1]: *** [CMakeFiles/ros_cv_gui_demo_node.dir/all] Error 2
make: *** [all] Error 2

[RH-Song]

I got the same problem. Have you solved it?