Stations tab causing "Internal Server Error"

[jgmtfia]

Just updated my install from GIT.  Everything seems to work ok - except when selecting the "stations" tab.  On the browser I get an  "Internal Server Error".  When running SIP from the command line I get:

Traceback (most recent call last):
  File "/home/pi/sip/web/application.py", line 239, in process
    return self.handle()
  File "/home/pi/sip/web/application.py", line 230, in handle
    return self._delegate(fn, self.fvars, args)
  File "/home/pi/sip/web/application.py", line 423, in _delegate
    return handle_class(cls)
  File "/home/pi/sip/web/application.py", line 399, in handle_class
    return tocall(*args)
  File "/home/pi/sip/webpages.py", line 254, in GET
    return template_render.stations()
  File "/home/pi/sip/web/template.py", line 1020, in template
    return self._base(t(*a, **kw))
  File "/home/pi/sip/web/template.py", line 881, in __call__
    return BaseTemplate.__call__(self, *a, **kw)
  File "/home/pi/sip/web/template.py", line 808, in __call__
    return self.t(*a, **kw)
  File "templates/stations.html", line 120, in __template__
    <input type="checkbox" ${"checked" if gv.sd['mo'][bid]&(1<<s) else ""} id="mc${sid}">
IndexError: list index out of range

192.168.2.29:40015 - - [24/Apr/2017 20:52:45] "HTTP/1.1 GET /vs" - 500 Internal Server Error


On a hunch I peeked at data/snames.json and everything looks reasonable (no sign of corruption):
["Front lawn", "Cherry Tree", "Flower Bed", "Northside Strip", "Rear Center Lawn", "Patio", "Rhubarb", "North Fence", "West Fence", "South Inside Fence", "South Outside Fence", "South Front", "S13", "S14", "S15", "S16"]


How can I help debug this bug?