Grid alpha value throws type error

[lgienapp]

with load_theme("arctic_light").set_grid(axis="x"):
    pd.Series(sizes).sort_values().plot.bar()

produces

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
/tmp/ipykernel_16842/1244744067.py in <module>
----> 1 with load_theme("arctic_light").set_grid(axis="x"):
      2     pd.Series(sizes).sort_values().plot.bar()

/media/ssd/BIGSCIENCE/env/lib/python3.7/site-packages/aquarel/theme.py in set_grid(self, draw, axis, ticks, alpha, style, width)
    432                 "axis": axis if axis in self._axis_options else None,
    433                 "ticks": ticks if ticks in self._tick_options else None,
--> 434                 "alpha": alpha if 0 <= alpha <= 1 else None,
    435                 "style": style if style in self._line_style_options else None,
    436                 "width": width,

TypeError: '<=' not supported between instances of 'int' and 'NoneType'