REST API does not allow nullifying all properties in a complex

1. in Studio create a custom document type customSchemaDoc with a custom schema containing a complex including 3 String properties
2. generate forms in Designer for the document type
3. install Nuxeo
4. create a document of type customSchemaDoc
5. set values for the 3 properties in the complex field (val1, val2, val3)
6. through REST try to set the properties as null (see the mycustomschema:myComplexThing section):

   curl -u Administrator:Administrator -X PUT \
     http://localhost:8080/nuxeo/api/v1/id/d59d8b39-17bc-4caa-9602-0d5a7b667fd7 \
     -H 'Cache-Control: no-cache' \
     -H 'Content-Type: application/json' \
     -H 'X-NXproperties: *' \
     -H 'uid: Administrator' \
     -d '{
       "entity-type": "document",
       "repository": "default",
       "uid": "d59d8b39-17bc-4caa-9602-0d5a7b667fd7",
       "path": "/default-domain/workspaces/testWorkspace23423/mytestdoccplx",
       "type": "customSchemaDoc",
       "state": "project",
       "properties": {
           "dc:description": "truc muche description",
           "mycustomschema:myComplexThing" : {
               "myAttrBla1" : null,
               "myAttrBla2" : null,
               "myAttrBla3" : null
           }
       }
   }'|json_pp
   

   This does not work and displays the following:

   {
      "state" : "project",
      "facets" : [],
      "isCheckedOut" : true,
      "changeToken" : "20-0",
      "uid" : "d59d8b39-17bc-4caa-9602-0d5a7b667fd7",
      "title" : "mytestdoccplx",
      "properties" : {
         "dc:lastContributor" : "Administrator",
         "common:icon" : null,
         "uid:minor_version" : 0,
         "dc:modified" : "2018-07-02T13:32:50.124Z",
         "dc:nature" : null,
         "dc:title" : "mytestdoccplx",
         "uid:uid" : null,
         "dc:created" : "2018-07-02T12:58:54.027Z",
         "dc:issued" : null,
         "mycustomschema:myComplexThing" : {
            "myAttrBla1" : "val1",
            "myAttrBla3" : "val3",
            "myAttrBla2" : "val2"
         },
         "dc:creator" : "Administrator",
         "dc:source" : null,
         "uid:major_version" : 0,
         "dc:format" : null,
         "dc:description" : "truc muche description",
         "common:icon-expanded" : null,
         "dc:publisher" : null,
         "dc:language" : null,
         "dc:contributors" : [
            "Administrator"
         ],
         "dc:expired" : null,
         "dc:rights" : null,
         "dc:coverage" : null,
         "dc:subjects" : [],
         "dc:valid" : null
      },
      "isProxy" : false,
      "repository" : "default",
      "entity-type" : "document",
      "isVersion" : false,
      "lastModified" : "2018-07-02T13:32:50.124Z",
      "parentRef" : "a1858390-ee7d-4b5d-bdd0-5971ea8a3714",
      "path" : "/default-domain/workspaces/testWorkspace23423/mytestdoccplx",
      "type" : "customSchemaDoc"
   }
   

7. Now try the same with at least one value and the rest set to null:

   curl -u Administrator:Administrator -X PUT \
     http://localhost:8080/nuxeo/api/v1/id/d59d8b39-17bc-4caa-9602-0d5a7b667fd7 \
     -H 'Cache-Control: no-cache' \
     -H 'Content-Type: application/json' \
     -H 'X-NXproperties: *' \
     -H 'uid: Administrator' \
     -d '{
       "entity-type": "document",
       "repository": "default",
       "uid": "d59d8b39-17bc-4caa-9602-0d5a7b667fd7",
       "path": "/default-domain/workspaces/testWorkspace23423/mytestdoccplx",
       "type": "customSchemaDoc",
       "state": "project",
       "properties": {
           "dc:description": "truc muche description",
           "mycustomschema:myComplexThing" : {
               "myAttrBla1" : "hop",
               "myAttrBla2" : null,
               "myAttrBla3" : null
           }
       }
   }'|json_pp
   

   This works as expected:

   {
      "path" : "/default-domain/workspaces/testWorkspace23423/mytestdoccplx",
      "isVersion" : false,
      "repository" : "default",
      "type" : "customSchemaDoc",
      "title" : "mytestdoccplx",
      "state" : "project",
      "parentRef" : "a1858390-ee7d-4b5d-bdd0-5971ea8a3714",
      "changeToken" : "21-0",
      "isProxy" : false,
      "uid" : "d59d8b39-17bc-4caa-9602-0d5a7b667fd7",
      "isCheckedOut" : true,
      "properties" : {
         "dc:creator" : "Administrator",
         "dc:valid" : null,
         "common:icon" : null,
         "dc:title" : "mytestdoccplx",
         "uid:major_version" : 0,
         "dc:publisher" : null,
         "dc:description" : "truc muche description",
         "dc:coverage" : null,
         "common:icon-expanded" : null,
         "dc:expired" : null,
         "dc:source" : null,
         "uid:minor_version" : 0,
         "dc:lastContributor" : "Administrator",
         "dc:contributors" : [
            "Administrator"
         ],
         "dc:modified" : "2018-07-02T13:34:02.324Z",
         "uid:uid" : null,
         "dc:issued" : null,
         "dc:created" : "2018-07-02T12:58:54.027Z",
         "dc:subjects" : [],
         "dc:format" : null,
         "dc:rights" : null,
         "mycustomschema:myComplexThing" : {
            "myAttrBla1" : "hop",
            "myAttrBla2" : null,
            "myAttrBla3" : null
         },
         "dc:language" : null,
         "dc:nature" : null
      },
      "lastModified" : "2018-07-02T13:34:02.324Z",
      "entity-type" : "document",
      "facets" : []
   }
   

Expected behavior: all the values should be updated even if the new values are all null.

This issue happens with the WebUI.

Note: it seems one value must not be null to make this work.
Note 2: package is attached for faster reproduction.