Omnicompletion crashes vim

[tusj]

I tried the omnicompletion by setting g:lua_complete_omni = 1 and installing vim-misc.

Running from terminal, I get:
(gvim:19321): GLib-GObject-WARNING **: cannot register existing type 'GdkWindow'

(gvim:19321): GLib-CRITICAL **: g_once_init_leave: assertion 'result != 0' failed

(gvim:19321): Gtk-ERROR **: GTK+ 2.x symbols detected. Using GTK+ 2.x and GTK+ 3 in the same process is not supported
Vim: Caught deadly signal TRAP
Vim: Finished.

So, gvim closes immediately when hitting C-X C-O. I get the same error in vim, just except the gtk warnings.