GraphSheet needs a default help_sidebars.

[anjakefala]

Small description

vd -p tests/graphPR-nosave.vd

And then press b to toggle sidebar.

You get this error:

Traceback (most recent call last):
  File "/home/anja/git/visidata/visidata/sidebar.py", line 115, in drawSidebar
    sidebar, title = sheet.help_sidebars[vd.disp_help%len(sheet.help_sidebars)]()
                                         ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
ZeroDivisionError: integer modulo by zero

Apparently, there are 0 sheet.help_sidebars on GraphSheet.