Move null condition to top.

src/main/java/com/kobylynskyi/graphql/codegen/mapper/ValueMapper.java

@@ -121,6 +121,9 @@ public class ValueMapper {
     }
 
     private String mapEnum(MappingContext mappingContext, EnumValue value, Type<?> graphQLType) {
+        if (graphQLType == null) {
+            return value.getName();
+        }
         if (graphQLType instanceof TypeName) {
             String typeName = ((TypeName) graphQLType).getName();
             typeName = DataModelMapper.getModelClassNameWithPrefixAndSuffix(mappingContext, typeName);
@@ -129,9 +132,6 @@ public class ValueMapper {
         if (graphQLType instanceof NonNullType) {
             return mapEnum(mappingContext, value, ((NonNullType) graphQLType).getType());
         }
-        if (graphQLType == null) {
-            return value.getName();
-        }
         throw new IllegalArgumentException("Unexpected Enum value for list type");
     }