Fix cast exception in integration test

- Although the class only has fields of Property type it would appear that CircleCI et al. may use libraries that add fields to classes later on, so we need to check for the field type

src/test/java/fr/xephi/authme/settings/custom/NewSettingIntegrationTest.java

@@ -35,12 +35,14 @@ public class NewSettingIntegrationTest {
     public static void generatePropertyMap() {
         propertyMap = new PropertyMap();
         for (Field field : TestConfiguration.class.getDeclaredFields()) {
-            Property<?> property =
-                (Property<?>) ReflectionTestUtils.getFieldValue(TestConfiguration.class, null, field.getName());
+            Object fieldValue = ReflectionTestUtils.getFieldValue(TestConfiguration.class, null, field.getName());
+            if (fieldValue instanceof Property<?>) {
+                Property<?> property = (Property<?>) fieldValue;
                 String[] comments = new String[]{"Comment for '" + property.getPath() + "'"};
                 propertyMap.put(property, comments);
             }
         }
+    }
 
     @Test
     public void shouldLoadAndReadAllProperties() {