Skip rendering None in all situations

[rmorshea]

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Issues

Currently the value None will render as the string "None" when used as a child in VDOM elements. However, when returned by a component it will not render. This inconsistency is confusing for users.

fix #1025

Solution

We should skip rendering None in all cases.

Checklist

• [X] Tests have been included for all bug fixes or added functionality.
• [X] The changelog.rst has been updated with any significant changes.