bugtimetracker fails after clicking "plot"

Title: bugtimetracker fails after clicking "plot"

Summary:
When clicking "plot" to plot a graph within bugtimetracker, nothing happens, and the following is shown in the logs:

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/bugtimetracker/application.py", line 292, in plot_cb
    data)
  File "/usr/lib/python2.7/dist-packages/bugtimetracker/plot.py", line 24, in __init__
    self.window.set_title(title)
  File "/usr/lib/python2.7/dist-packages/bugtimetracker/widget.py", line 35, in __getattr__
    raise AttributeError, name
AttributeError: window

Steps:
1) Install bugtimetracker
2) Open a project in bugtimetracker
3) Click plot

Expected results: A graph is created?

Actual results: Nothing happens

CPU: Intel(R) Core(TM) i5-2520M CPU @ 2.50GHz (4x)

GPU: 00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09)

Manufacturer: LENOVO

ProductName: 4170CTO

BiosVersion: 8CET32WW (1.09 )