Dotted line is not shown on a legend item with larger size

In the legend customized by `override_aes`, `linetype` does not work well for larger values of the `size` parameter and `linewidth` has no effect.
```
ggplot() + \
geom_rect(aes(xmin=[0], xmax=[1], ymin=[0], ymax=[1], fill=["0"])) + \
guides(fill=guide_legend(override_aes={'alpha': 0.5, 'size': 10, 'linewidth': 5, 'linetype': 2}))
```
The border of the legend item is not dotted and the line width is not 5.