field mapping of a field of an embedded object is not taken into account if value of this field is unset

[ptitcoutu]

In org.grails.datastore.mapping.mongo.engine.codecs.PersistentEntityCodec line 264 there's a code which should unset a field but the code use the property name of the entity instead of the field name of the mapping defined in GORM

So the code should use prop.mappedForm.targetName instead of prop.name

The code is the same in the most recent version of the class so the issue is still here

Context :
Grails : 4.0.0
GORM : 7.0.0.RELEASE
Groovy : 2.5.6

[puneetbehl]

Please feel free to send a PR!