Make compatible with GF 3.6 and latest GF-Estonian

The following tests now fail producing `Ix{Int}.index: Index (-1) out of range ((0,-1))`
(did not investigate why):

```
l PLanguage Flemish
l PLanguage (LangNat Swedish)
l PCitizenship Belgian
l PCitizenship (CitiNat Dutch)
l PCountry Belgium
l PCountry (CountryNat Polish)
```