"Joystick was not initialized in the constructor" is not an error. It is a warning. You should still be able to build (FRCUserProgram file should still appear under Binaries).
I can reproduce this by creating a new Commandbased C++ project, adding a Joystick * joystick to IO header and heap allocating it in the constructor just as you have.
Clean the project, rebuild the index, right-click delete the errors and warnings in the "Problems" Tab, then full-rebuild.
At this point the warning will be gone.
You will will still see this warning...
Code:
libstdc++.so.6, needed by :\Users\ozrie_000/wpilib/cpp/current/lib\libFRC_NetworkCommunication.so.1.5.0
... that's ok, you should still get a new FRCUserProgram executable.