fill_alpha of labels not respected when plotting purely outline #240
Description
Currently with the cosmx notebook I noticed in the example that when trying to only plot the outline by setting outline to True and fill_alpha to 0 no labels are plotted at all including the contours of the labels. When the fill_alpha is between 0 and 1, the behaviour is as expected. However when the fill_alpha is 1 when outline is set to True then only the outline is shown.
Note it is more correct to say, purely the outline is shown when the fill_alpha is equal to outline_alpha when outline is set to True.