ValueError on empty ticker data

[bitphage]

  File "/home/vvk/devel/bitshares/bitshares-pricefeed/bitshares_pricefeed/pricefeed.py", line 376, in compute_target_price
    ticker = Market("%s:%s" % (backing_symbol, symbol)).ticker()
  File "/home/vvk/.local/share/virtualenvs/bitshares-pricefeed-DCueNqwP/lib/python3.6/site-packages/bitshares/market.py", line 153, in ticker
    ticker["base_volume"], self["base"], blockchain_instance=self.blockchain
  File "/home/vvk/.local/share/virtualenvs/bitshares-pricefeed-DCueNqwP/lib/python3.6/site-packages/graphenecommon/instance.py", line 34, in __init__
    cls.__init__(self, *args, **kwargs)
  File "/home/vvk/.local/share/virtualenvs/bitshares-pricefeed-DCueNqwP/lib/python3.6/site-packages/graphenecommon/amount.py", line 132, in __init__
    self["amount"] = float(self["amount"])
ValueError: could not convert string to float: 

Raw ticker data, the asset is newly created:

{'time': '1970-01-01T00:00:00', 'base': '', 'quote': '', 'latest': '', 'lowest_ask': '', 'highest_bid': '', 'percent_change': '', 'base_volume': '', 'quote_volume': ''}