No visible binding for global variable in ShapeToMask()

Hi @vagudets,

The CMD check returns a NOTE complaining that:

- .polygonize: no visible binding for global variable ‘geometry’ 
- .shapetomask: no visible binding for global variable ‘geometry’ 
- .shapetomask: no visible binding for global variable ‘value’ 
- .shapetomask: no visible binding for global variable ‘int’

If these variables are used deliberately "unbound", an option seems to add utils::globalVariables() https://www.rdocumentation.org/packages/utils/versions/3.6.2/topics/globalVariables, before defining ShapeToMask()):

utils::globalVariables(c("geometry", "value", "int"))
ShapeToMask <- function(...) {...}

Let me know what you think.

Thanks in advance,

Ariadna