Allow font-family to be inherited if font.family is set to empty

[zeripath]

I'm unsure whether this would work in all output formats, but it would be good to not have to set the font-family explicitly for flextable and instead just inherit directly from the css/styling outside of the flextable.

I propose, that either, one sets the font.family to "" (or NA) and then in runs_as_functions.R change:

flextable/R/runs_as_functions.R

Line 10 in 39d8214

family <- sprintf("font-family:'%s';", x$font.family)

to simply detect if it's "", e.g.:

family <- ""
if (x$font.family != "") {
  family <- sprintf("font-family:'%s';", x$font.family) 
}

or for NA:

family <- ""
if (!is.na(x$font.family) {
  family <- sprintf("font-family:'%s';", x$font.family) 
}

AFAIC The font-family should then simply be inherited from the rest of the document.