[node:edit] (Multi-value) references not being serialized propertly

[dantleech]

Not possible to edit and save node with multi-value REFERENCE properties.

# Error encounred: 
# Errors encountered during denormalization: Can not determine type of property with value "NULL"
# 
'jcr:primaryType':
    type: Name
    value: 'nt:unstructured'
'i18n:de-creator':
    type: Long
    value: 1
'i18n:de-created':
    type: Date
    value: null
'jcr:mixinTypes':
    type: Name
    value: ['sulu:page']
'i18n:de-changer':
    type: Long
    value: 1
'i18n:de-changed':
    type: Date
    value: null
'i18n:de-template':
    type: String
    value: hotel_page
'i18n:de-nodeType':
    type: Long
    value: 1
'i18n:de-state':
    type: Long
    value: 2
'i18n:de-published':
    type: Date
    value: null
'i18n:de-title':
    type: String
    value: 'Hotels page'
'i18n:de-hotels':
    type: Reference
    value: { 8c6596a2-c8be-4ab6-a537-6bc09ec311a6: null, b340e222-81d3-4cd1-91e3-4d738cf2d9b7: null }
'jcr:uuid':
    type: String
    value: 419f1f06-e16f-43fe-8583-2a27d375fe1e
'sulu:order':
    type: Long
    value: 20

[dantleech]

Also spelling mistake for "errors encounred" above.

[dantleech]

Fixed.