Undefined field _text_

If you get the error:

Undefined field _text_

Please make sure to open up solrconfig.xml in your Opensolr Control Panel Admin UI and remove the reference to the _text_ field under the /update initParams:

<initParams path="/update/**,/query,/select,/tvrh,/elevate,/spell,/browse">
    <lst name="defaults"></lst>
    <str name="df">_text_</str>
</initParams>