fix popup sticky options

[Conengmo]

Fix #2047

This is a similar issue to #2043, happening after the v0.19.0 release, caused by changes in #2029.

Fix it by using proper boolean values for these options on Popup, not None values.

[Conengmo]

@hansthen I'm not sure if we're going the right way by addressing these individually. Looking at https://github.com/python-visualization/folium/pull/2029/files there are lots of places where parse_options was removed, but the default arguments are None, so we are adding null options that were not there before. That means potentially lots more issues like this one.

I think we should go with a simple solution for now, because we have a release out and I'd like to avoid people getting bit by this. Maybe either:

• remove None arguments in tojavascript
• revert Issue 1943 allow jscode in options #2029

For that first solution, do you reckon that will lead to issues? Is there a use for explicit null arguments in Leaflet?

[hansthen]

I would prefer to leave None values in the tojavascript because null values are part of the json spec. My feeling is that tojavascript is more generic than the original parse_options, even though it largely serves the same function. Also, I can't exclude the possibility that Leaflet options can be validly null.

I am open to reverting #2029 for now and do a proper release later. However, I did make a simple fix that again removes None values from the options. You could have a look at that to see if you think it is a viable solution. I still have to fix four tests though.

[Conengmo]

Close in favor of #2049