Fixed bugs with forking ThangTypes.

app/models/CocoModel.coffee

@@ -96,7 +96,9 @@ class CocoModel extends Backbone.Model
   schema: -> return @constructor.schema
 
   getValidationErrors: ->
-    errors = tv4.validateMultiple(@attributes, @constructor.schema or {}).errors
+    # Since Backbone unset only sets things to undefined instead of deleting them, we ignore undefined properties.
+    definedAttributes = _.pick @attributes, (v) -> v isnt undefined
+    errors = tv4.validateMultiple(definedAttributes, @constructor.schema or {}).errors
     return errors if errors?.length
 
   validate: ->

app/views/editor/ForkModal.coffee

@@ -31,7 +31,7 @@ module.exports = class ForkModal extends ModalView
     newModel.unset 'parent'
     newModel.set 'commitMessage', "Forked from #{@model.get('name')}"
     newModel.set 'name', @$el.find('#fork-model-name').val()
-    if @model.schema.properties.permissions
+    if @model.schema().properties.permissions
       newModel.set 'permissions', [access: 'owner', target: me.id]
     newPathPrefix = "editor/#{@editorPath}/"
     res = newModel.save()

app/views/modal/NewModelModal.coffee

@@ -28,7 +28,7 @@ module.exports = class NewModelModal extends ModalView
     model = new @model
     name = @$el.find('#name').val()
     model.set('name', name)
-    if @model.schema.properties.permissions
+    if @model.schema().properties.permissions
       model.set 'permissions', [{access: 'owner', target: me.id}]
     model.set(key, prop) for key, prop of @properties if @properties?
     model