fix: dont check bool dtype until after ndarray conversion

[scottstanie]

This appears to fix #411

In [1]: import proplot as pplt
import numpy as np

In [2]: import numpy as np

In [3]: fig, ax = pplt.subplot()
   ...: ax.plot(np.arange(10))
Out[3]: <a list of 1 Line2D objects>

@syrte Feel free to check on this if you have other

[lukelbd]

Sorry, awkward timing -- just submitted a fix myself (see issue thread). Appreciate the contribution though.

And thanks for the test. I am currently working on adding lots of unit tests to the CI workflow; will add your function to these.

[scottstanie]

oh great, no problem! that timing was so exact that it confused me how my branch suddenly had merge conflicts haha