"NA" in strings should not be NA

[Simon J Greenhill]

Noticed in glottolog-cldf:

> g$tables$LanguageTable %>% filter(Countries == 'NA')
# no rows found.. .and languages in Namibia are coded as NA (=missing):

> g$tables$LanguageTable %>% filter(ID == 'mbal1255')
# A tibble: 1 × 13
  ID       Name  Macro…¹ Latit…² Longi…³ Glott…⁴ ISO63…⁵ Count…⁶ Famil…⁷ Langu…⁸
  <chr>    <chr> <chr>     <dbl>   <dbl> <chr>   <chr>   <chr>   <chr>   <chr>
1 mbal1255 Cent… Africa    -17.6    16.0 mbal12… lnb     NA      atla12… NA

[Simon J Greenhill]

fixed in 1fd0536