change default argument reactive(NULL)

[nikolas-burkoff]

Closes #178

• I prefer reactive(NULL) than NULL
• We are limited in what we do in initialize as if we check the value of x_reactive then we need isolate around the constructor
• I'm open to suggestions regarding making this nicer
• Added the css into the filterstates ui as well as we need it for the RangeFilterState histograms

Default of FilterStates is also reactive(NULL)

[nikolas-burkoff]

I guess if we change from reactive(NULL) to just NULL we can do something smarter in initialize as then the check if(is.null(x_reactive)) doesn't need an isolate...

[gogonzo]

I think these get_choices_label functions are too complicated. I think we can simplify and tidy up the way how we obtain counts. In the init of choicesFilterState there is private$histogram_data which isn't used at all. Having private$choices where value is a factor level and name is a count is also not elegant. I think we can introduce

private$choices # factor levels
private$choices_count # unfiltered count
private$f_choices_count # reactive
private$calculate_choices_count(x) 

That is just a proposition, I think it would be nice if we tidy up these initialize methods and how we preserve counts.

Issue #183

[gogonzo]

👍 Thanks