Fixed a null check for the sortOrder parameter

src/main/java/nl/utwente/mod4/pokemon/routes/PokemonRoute.java

@@ -17,7 +17,7 @@ public class PokemonRoute {
     public List<Pokemon> getPokemon(@QueryParam("sortBy") String sortOrder) {
         Integer pageSize = Integer.MAX_VALUE;
         List<Pokemon> pokemons =  PokemonDao.INSTANCE.getPokemon(pageSize, 1);
-        if (sortOrder.equals("name")) {
+        if (sortOrder != null && sortOrder.equals("name")) {
             pokemons.sort(Comparator.comparing(pok -> pok.name));
         }