@kazurayam that was based on the assumption that the null result was causing the other exception, the fix was not resolved at that time. But i did find a workaround, see last comment.
Why the DevTools processes class="..." and value="..." differently?
In the W3C Hypertext Markup Language specification, it is clearly written that the VALUE attribute in <input type="text" value="xxxx"> is the initial value of the field. In other words, the new texts typed by human or changed by javascripts — these are not supposed to be he VALUE.
OK. DevTools is behaving as per the W3C HTML spec. My question is now resolved.