Using g:render with model attribute set inside f:with tags throws java.util.EmptyStackException

```

throws excepstion at:
Around line 80 of grails-app/taglib/grails/plugin/formfields/FormFieldsTagLib.groovy

77: beanStack.push(beanPrefix)
78: out << body()
79: } finally {
80: beanStack.pop()
81: }
82: }
```

Start with the reproduction using f:with and g:render, then inspect grails-app/taglib/grails/plugin/formfields/FormFieldsTagLib.groovy around lines 77-81, where beanStack is pushed, used, and popped. Confirm the EmptyStackException and determine what behavior should prevent it; done means the example renders without that exception.

Written by the indexing model from the issue text.