Button elements render with a value attribute even when the value is null or undefined

[svensigmond]

Describe the bug
The conditional attribute functionality seems to be broken for buttons when it comes to the value attribute.

Button elements render with a value attribute even if the value is null or undefined.

To Reproduce
Please consider the following example:
https://svelte.dev/repl/dc5009fbb5a242b583de400e0df3c99b?version=3.24.0

Please inspect the first button and notice that it contains a value attribute and the attribute is set to null

Expected behavior
The button should not have a value attribute because its value is null. The same should go for undefined.

This does not match the conditional functionality as explained by Conduitry in the following comment:
#259 (comment)

Information about your Svelte project:

• Svelte version (3.24.0 REPL)

Severity
Annoying

Additional context
It is my understanding that the conditional behaviour only applies to valid html element attributes. Value is a valid attribute, so I suspect this is a simple oversight:

https://html.spec.whatwg.org/multipage/form-elements.html#the-button-element

[mindrones]

Seems related to #4467

[dummdidumm]

Closing as duplicate of #4467 , which also notes the inconsistencies.