canvas.copy() triggers exception

[smathot]

When calling canvas.copy() with any back-end, the following Exception is triggered:

"File "dist\libopensesame\inline_script.py", line 96, in run
  File "dist\libopensesame\python_workspace.py", line 160, in _exec
  File "<string>", line 32, in <module>
  File "dist\openexp\_canvas\xpyriment.py", line 61, in copy
TypeError: set_config() takes exactly 1 argument (2 given)"

This appears to be due to not unpacking a keyword dict.