Avoid NPE in DefaultTransientPropertyResolverService

Existing code caused NPE when type did not extend Object class.
This is the case with interfaces, such as java.util.Map.

nrich-webmvc/src/main/java/net/croz/nrich/webmvc/service/DefaultTransientPropertyResolverService.java

@@ -33,7 +33,7 @@ public List<String> resolveTransientPropertyList(Class<?> type) {
         List<String> transientPropertyList = new ArrayList<>();
         Class<?> currentType = type;
 
-        while (currentType != Object.class) {
+        while (currentType != null && currentType != Object.class) {
             List<String> currentTransientPropertyList = Arrays.stream(currentType.getDeclaredFields())
                 .filter(this::includeField)
                 .map(Field::getName)

nrich-webmvc/src/test/java/net/croz/nrich/webmvc/service/DefaultTransientPropertyResolverServiceTest.java

@@ -24,8 +24,10 @@
 import org.springframework.test.context.junit.jupiter.web.SpringJUnitWebConfig;
 
 import java.util.List;
+import java.util.Map;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.catchThrowable;
 
 @SpringJUnitWebConfig(WebmvcTestConfiguration.class)
 class DefaultTransientPropertyResolverServiceTest {
@@ -44,4 +46,13 @@ void shouldResolveTransientPropertyList() {
         // then
         assertThat(resultList).containsExactlyInAnyOrder("value", "anotherValue");
     }
+
+    @Test
+    void shouldNotFailWhenResolvingTransientPropertyListFromInteface() {
+        // when
+        Throwable thrown = catchThrowable(() -> transientPropertyResolverService.resolveTransientPropertyList(Map.class));
+
+        // then
+        assertThat(thrown).isNull();
+    }
 }