Bug report

Bug summary

Setting the lower rlim of polar plots with set_rlim(bottom=...) is particularly useful given #13292, but got broken in #12300 (master only, attn @jklymak).

Code for reproduction

polar([1, 2]); gca().set_rlim(bottom=.5)

Actual outcome

Traceback (most recent call last):
  File "<string>", line 4, in <module>
  File "matplotlib/lib/matplotlib/projections/polar.py", line 1153, in set_rlim
    **kwargs)
  File "matplotlib/lib/matplotlib/projections/polar.py", line 1205, in set_ylim
    if top is None and len(bottom) == 2:
TypeError: object of type 'float' has no len()

Expected outcome

no error (which is the case as of mpl 3.0)

Matplotlib version

• Operating system:
• Matplotlib version: master
• Matplotlib backend (print(matplotlib.get_backend())):
• Python version:
• Jupyter version (if applicable):
• Other libraries: