Vue does not accept undefined values when returning an array in functional component

[sqal]

Version

2.5.11

Reproduction link

https://jsfiddle.net/qL80y6oL/

Steps to reproduce

Check console log.

What is expected?

Should render input element

What is actually happening?

When functional component returns an array and the array contains other values besides vnodes like e.g. null or undefined Vue will not render anything and throw an error.

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I checked this in few previous versions and it seems that it never worked correctly. In 2.5.9 I get a different warning "Cannot set property 'isRootInsert' of null". So the question is. Is this a case that should be handled by Vue internally, or do I have to be careful and not to return null/undefined values in returned array.

[posva]

The array must contain vnodes, so only things created with h (or createElement) but it's weird because I was expecting to find more information in the typings but we only allow returning vnode there, not arrays so now I don't know if the typing are wrong and this was never intended or if it was just forgotten for the typings