handle aes( ... = NULL) appropriately

ggplotly does not accept aesthetics with NULL assignment.
Use case in a programmatic big app I have a code that assigns aesthetics globally then turn off the aesthetics for some layers.
There are some workarounds but my issue I am filing in here is to handle correctly the aes ( ... = NULL)

require(ggplot2)
require(plotly)

plottest<- ggplot(mtcars,aes(mpg,disp))+
  aes(group=cyl)+
  geom_line()+
  geom_smooth(aes(group=NULL))

ggplotly(plottest)

plotfixed<- ggplot(mtcars,aes(mpg,disp))+
  geom_line(aes(group=cyl) )+
  geom_smooth()

ggplotly(plotfixed)

Start by running the supplied R examples with ggplot2 and plotly, comparing the global group aesthetic with the layer using aes(group=NULL). Trace how ggplotly handles that layer and verify that the NULL assignment disables the inherited aesthetic without breaking conversion.