GFiles error

- [x] I have read through https://github.com/junegunn/fzf.vim/blob/master/README.md
- [x] I have read through https://github.com/junegunn/fzf/blob/master/README-VIM.md
- [x] I have read through the manual page of fzf (`man fzf`)
- [x] I have searched through the existing issues

```
Error running ( git ls-files | uniq )|'/tmp/plugged/fzf/bin/fzf' -m --prompt "GitFiles> " '--preview-window' 'right' '--preview' ''\''/tmp/plugged/fzf.vim/bin/preview.sh'\'' {}' --expect=ctrl-v,ctrl-x,ctrl-t --height=33 > /tmp/user/1160775374/vePLWGr/17
```

In my terminal, `( git ls-files | uniq )|'/tmp/plugged/fzf/bin/fzf' -m --prompt "GitFiles> " ` works as intended

in vim, `:FZF` works too, suggesting fzf vim plug installation was done correctly

I'm using vim-gtk3 (8.2) from jonathon.fernyhough's PPA:

```
$ vim --version
VIM - Vi IMproved 8.2 (2019 Dec 12, compiled Jun 21 2020 13:27:13)
Included patches: 1-1027
Modified by jonathon.fernyhough@york.ac.uk
Compiled by jonathon.fernyhough@york.ac.uk
Huge version with GTK3 GUI. Features included (+) or not (-):
+acl -farsi +mouse_sgr +tag_binary
+arabic +file_in_path -mouse_sysmouse -tag_old_static
+autocmd +find_in_path +mouse_urxvt -tag_any_white
+autochdir +float +mouse_xterm +tcl
-autoservername +folding +multi_byte +termguicolors
+balloon_eval -footer +multi_lang +terminal
+balloon_eval_term +fork() -mzscheme +terminfo
+browse +gettext +netbeans_intg +termresponse
++builtin_terms -hangul_input +num64 +textobjects
+byte_offset +iconv +packages +textprop
+channel +insert_expand +path_extra +timers
+cindent +ipv6 +perl +title
+clientserver +job +persistent_undo +toolbar
+clipboard +jumplist +popupwin +user_commands
+cmdline_compl +keymap +postscript +vartabs
+cmdline_hist +lambda +printer +vertsplit
+cmdline_info +langmap +profile +virtualedit
+comments +libcall -python +visual
+conceal +linebreak +python3 +visualextra
+cryptv +lispindent +quickfix +viminfo
+cscope +listcmds +reltime +vreplace
+cursorbind +localmap +rightleft +wildignore
+cursorshape +lua +ruby +wildmenu
+dialog_con_gui +menu +scrollbind +windows
+diff +mksession +signs +writebackup
+digraphs +modify_fname +smartindent +X11
+dnd +mouse +sound -xfontset
-ebcdic +mouseshape +spell +xim
+emacs_tags +mouse_dec +startuptime +xpm
+eval +mouse_gpm +statusline +xsmp_interact
+ex_extra -mouse_jsbterm -sun_workshop +xterm_clipboard
+extra_search +mouse_netterm +syntax -xterm_save
system vimrc file: "$VIM/vimrc"
user vimrc file: "$HOME/.vimrc"
2nd user vimrc file: "~/.vim/vimrc"
user exrc file: "$HOME/.exrc"
system gvimrc file: "$VIM/gvimrc"
user gvimrc file: "$HOME/.gvimrc"
2nd user gvimrc file: "~/.vim/gvimrc"
defaults file: "$VIMRUNTIME/defaults.vim"
system menu file: "$VIMRUNTIME/menu.vim"
fall-back for $VIM: "/usr/share/vim"
Compilation: gcc -std=gnu99 -c -I. -Iproto -DHAVE_CONFIG_H -DFEAT_GUI_GTK -pthread -I/usr/include/gtk-3.0 -I/usr/include/atk-1.0 -I/usr/include/at-spi2-atk/2.0 -I/usr/include/pango-1.0 -I/usr/include/gio-unix-2.0/ -I/usr/include/cairo -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include -I/usr/include/harfbuzz -I/usr/include/freetype2 -I/usr/include/pixman-1 -I/usr/include/libpng12 -g -O2 -fPIE -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security -D_REENTRANT -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1
Linking: gcc -std=gnu99 -L. -Wl,-Bsymbolic-functions -Wl,-z,relro -L/build/ruby1.9.1-E8yHvR/ruby1.9.1-1.9.3.484/debian/lib -rdynamic -Wl,-export-dynamic -Wl,-E -Wl,-Bsymbolic-functions -fPIE -pie -Wl,-z,relro -Wl,-z,now -Wl,--as-needed -o vim -lgtk-3 -lgdk-3 -latk-1.0 -lgio-2.0 -lpangocairo-1.0 -lgdk_pixbuf-2.0 -lcairo-gobject -lpango-1.0 -lcairo -lgobject-2.0 -lglib-2.0 -lSM -lICE -lXpm -lXt -lX11 -lXdmcp -lSM -lICE -lm -ltinfo -lselinux -lcanberra -lacl -lattr -lgpm -ldl -L/usr/lib -llua5.2 -Wl,-E -fstack-protector -L/usr/local/lib -L/usr/lib/perl/5.18/CORE -lperl -ldl -lm -lpthread -lcrypt -L/usr/lib/python3.4/config-3.4m-x86_64-linux-gnu -lpython3.4m -lpthread -ldl -lutil -lm -L/usr/lib/x86_64-linux-gnu -ltcl8.6 -ldl -lz -lpthread -lieee -lm -lruby-1.9.1 -lpthread -lrt -ldl -lcrypt -lm -L/usr/lib
```

Note that this is on my brand new computer. On my old computer this was working just fine. I copied the .vimrc between the 2 and installed vim from the same PPA. Note that the error I posted above occurred when running with the `vim -Nu` command you suggested.

I can't find any error message detailing what the error could be, so I have no idea how to troubleshoot this further. I hope you'll find the time to help me.