Sometimes integral(multiplySeries(foo.bar,foo.baz)) fails to render.

[Nicholas Leskiw]

...
I want to total the time up over the past four hours, so I tried integral(multiplySeries(x,y)) but just get a broken image icon.
Should this work, or am I misunderstanding how this is supposed to work?
...
stack trace:

Traceback (most recent call last):
  File "/usr/lib/python2.6/site-packages/django/core/handlers/base.py", line 111, in get_response
    response = callback(request, *callback_args, **callback_kwargs)
  File "/opt/graphite/webapp/graphite/render/views.py", line 104, in renderView
    seriesList = evaluateTarget(requestContext, target)
  File "/opt/graphite/webapp/graphite/render/evaluator.py", line 10, in evaluateTarget
    result = evaluateTokens(requestContext, tokens)
  File "/opt/graphite/webapp/graphite/render/evaluator.py", line 21, in evaluateTokens
    return evaluateTokens(requestContext, tokens.expression)
  File "/opt/graphite/webapp/graphite/render/evaluator.py", line 29, in evaluateTokens
    return func(requestContext, *args)
  File "/opt/graphite/webapp/graphite/render/functions.py", line 678, in integral
    for val in series:
TypeError: 'NoneType' object is not iterable

[Nicholas Leskiw (nleskiw)]

looks like multiplySeries returned a single series, but integral expects a list of series.

[Nicholas Leskiw (nleskiw)]

commit 47d90c6ab299b5b4976382021f85f0f7b2a08388
Author: Nicholas Leskiw <email address hidden>
Date: Mon Jul 9 15:31:25 2012 -0500

    Bugfix for https://bugs.launchpad.net/graphite/+bug/1021942

    integral(multiplySeries(x,y)) was failing to render a graph.

    Cause was intergral expects a seriesList, but multiplySeries only
    returned a single series.