SONAR-8004 WS settings/set fails when property set field with a null value

server/sonar-server/src/main/java/org/sonar/server/setting/ws/SetAction.java

@@ -216,7 +216,10 @@ public class SetAction implements SettingsWsAction {
       .map(oneFieldValues -> readOneFieldValues(oneFieldValues, request.getKey()))
       .flatMap(map -> map.entrySet().stream())
       .peek(entry -> valuesByFieldKeys.put(entry.getKey(), entry.getValue()))
-      .forEach(entry -> checkRequest(fieldKeys.contains(entry.getKey()), "Unknown field key '%s' for setting '%s'", entry.getKey(), request.getKey()));
+      .forEach(entry -> {
+        checkRequest(fieldKeys.contains(entry.getKey()), "Unknown field key '%s' for setting '%s'", entry.getKey(), request.getKey());
+        checkRequest(entry.getValue() != null, "Parameter field '%s' must not be null", entry.getKey());
+      });
 
     checkFieldType(request, definition, valuesByFieldKeys);
   }

server/sonar-server/src/test/java/org/sonar/server/setting/ws/SetActionTest.java

@@ -544,6 +544,29 @@ public class SetActionTest {
     callForGlobalPropertySet("my.key", newArrayList(GSON.toJson(ImmutableMap.of("field", "notAnInt"))));
   }
 
+  @Test
+  public void fail_when_property_set_has_a_null_field_value() {
+    propertyDefinitions.addComponent(PropertyDefinition
+      .builder("my.key")
+      .name("foo")
+      .description("desc")
+      .category("cat")
+      .subCategory("subCat")
+      .type(PropertyType.PROPERTY_SET)
+      .defaultValue("default")
+      .fields(newArrayList(
+        PropertyFieldDefinition.build("field")
+          .name("Field")
+          .type(PropertyType.STRING)
+          .build()))
+      .build());
+
+    expectedException.expect(BadRequestException.class);
+    expectedException.expectMessage("Parameter field 'field' must not be null");
+
+    callForGlobalPropertySet("my.key", newArrayList("{\"field\": null}"));
+  }
+
   @Test
   public void fail_when_property_set_with_invalid_json() {
     propertyDefinitions.addComponent(PropertyDefinition