The bug is reproduced as follows:
1. Use StatelessForm.
2. Use compound model, eg CompoundPropertyModel. In this case, form components are not initially aware of their model types.
3. Use any text component inside, eg TextField
1. In StatelessForm, form processing occurs BEFORE components were actually rendered.
2. BUT AbstractTextComponent guesses its model type ONLY in onBeforeRender().
3. onBeforeRender() never gets called, so text component doesn't know its actual type and cannot convert properly.
4. Everything crashes because of incorrect type (validators and form submission is working wrong).
Obviously, this processing sequence needs to be fixed (eg retrieve model type early or check for stateless forms explicitly).