selects render "undefined" when bound to a oneOf definition

for the following schema:

``` javascript{
"$schema": "http://json-schema.org/draft-04/schema#",
"type": "object",
"typeName": "IncomingFileIODto",
"additionalProperties": false,
"required": [
"EndPoint",
"Title",
"Comment",
"Status",
"OwnerBoxId"
],
"properties": {
"ChannelTypeName": {
"type": "string",
"readOnly": true
},
"ChannelTypeInfo": {
"type": "string",
"readOnly": true
},
"Title": {
"type": "string"
},
"Comment": {
"type": "string",
"format": "textarea"
},
"Status": {
"default": "Enabled",
"oneOf": [
{
"$ref": "#/definitions/ChannelState"
}
]
},
"EndPoint": {
"type": "string"
},
"Interval": {
"type": "integer"
},
"IntervalUnit": {
"oneOf": [
{
"$ref": "#/definitions/TimeUnit"
}
]
},
"DateTimeStart": {
"type": "string",
"format": "datetime-local"
},
"DateTimeStop": {
"type": "string",
"format": "datetime-local"
},
"DateTimeCreated": {
"type": "string",
"format": "datetime-local",
"readOnly": true
},
"DateTimeLastChanged": {
"type": "string",
"format": "datetime-local",
"readOnly": true
},
"TemporaryFolderName": {
"type": "string",
"readOnly": true
},
"ID": {
"type": "string",
"readOnly": true
},
"OwnerBoxId": {
"type": "integer",
"readOnly": true
}
},
"definitions": {
"ChannelState": {
"type": "string",
"typeName": "ChannelState",
"enumNames": [
"Disabled",
"Enabled",
"Paused",
"Errored"
],
"enum": [
"Disabled",
"Enabled",
"Paused",
"Errored"
],
"description": ""
},
"TimeUnit": {
"type": "string",
"typeName": "TimeUnit",
"enumNames": [
"Seconds",
"Minutes",
"Hours",
"Days",
"Weeks",
"Months",
"Years"
],
"enum": [
"Seconds",
"Minutes",
"Hours",
"Days",
"Weeks",
"Months",
"Years"
],
"description": ""
}
}
}
```

the select boxes rendered for the TimeUnit and Status types render a select box with only "undefined" as the available choice.
When selecting this undefined value, a new Select is immediately rendered beneath it which contains the correct options as defined in the schema.

When the bootstrap-select renderer is used, the behaviour is different. The select box renders no options and no drop down is displayed on click.

Reproduce the issue with the supplied JSON Schema, focusing on the select rendering path for oneOf references to TimeUnit and ChannelState. Compare the standard select renderer with the bootstrap-select renderer. Done means both fields show their schema-defined options directly, without an "undefined" option or a second nested select.

Written by the indexing model from the issue text.