Empty array breaks varstack

[mat813]

I have this:

foo: []

And it breaks with:

Traceback (most recent call last):
  File "/usr/local/bin/varstack", line 33, in <module>
    res = vs.evaluate(vardata)
  File "/usr/local/lib/python2.7/site-packages/varstack/__init__.py", line 59, in evaluate
    return self.__cleanupData(rawdata)
  File "/usr/local/lib/python2.7/site-packages/varstack/__init__.py", line 103, in __cleanupData
    newdata[key] = self.__cleanupData(data[key])
  File "/usr/local/lib/python2.7/site-packages/varstack/__init__.py", line 103, in __cleanupData
    newdata[key] = self.__cleanupData(data[key])
  File "/usr/local/lib/python2.7/site-packages/varstack/__init__.py", line 105, in __cleanupData
    if type(data[0]) == dict and '__combine' in data[0]:
IndexError: list index out of range