Feature Request: vlines argument None or False or ...

Hello @DanielGoldfarb,

Mplfinance is looking great and I have adopted it in my Example Notebook for my Pandas TA Library.

Is your feature request related to a problem? Please describe.
Simple value to pass into vlines argument so it passes without error.

Describe the solution you'd like
Some value like None or False or whatever you deem appropriate for the package requirements.

Describe alternatives you've considered
I created an invisible out of chart range data to bypass the error. It's a hack but seems unnecessary.

if amat_sr:
    vlines_ = dict(vlines=amat_sr, alpha=0.1, colors="
else:
    # Hidden because vlines needs valid arguments even if None 
    vlines_ = dict(vlines=mpfdf.index[0], alpha=0, colors="white")

Additional context
I made a semi-dynamic Panels Chart Class Example Notebook for my Pandas TA Library. The plot method is located at the bottom of Input Cell 11. You can play around with the Chart class arguments in Input Cell 12.

Thanks for your time,
Kevin

Start with the plot method at the bottom of Input Cell 11 in the linked example notebook and reproduce the chart with vlines set to None or False. Trace the vlines argument handling in mplfinance, then verify that an omitted or empty value passes without error and that the notebook still renders the chart.