Add JsonNull check for habitats in PokemonSpecies

Author: RaKXeR

src/main/java/eu/iamgio/pokedex/pokemon/PokemonSpecies.java

@@ -189,7 +189,7 @@ public static PokemonSpecies fromPokemonName(String pokemonName) throws PokedexE
                 pokedexNumbers,
                 Generation.fromJson(json),
                 evolvesFromSpecies.isJsonNull() ? null : new NamedResource(evolvesFromSpecies.getAsJsonObject()).getName(),
-                PokemonHabitat.valueOf(new NamedResource(json.get("habitat")).toEnumName()),
+                json.get("habitat").isJsonNull() ? null : PokemonHabitat.valueOf(new NamedResource(json.get("habitat")).toEnumName()),
                 NamedResource.getNames(json.getAsJsonArray("egg_groups"))
                     .stream()
                     .map(StringUtil::toEnumName)