"Invalid" Style section metadata prevents pages from rendering

[bstopp]

Expected Behaviour

if the author inputs a somewhat invalid section style metadata, it should not prevent the page from rendering.

Author adds the following, should still render:

Section Metadata
Style	blue background,

Actual Behaviour

Page fails to render due to an empty class name attempted to be added to the section class list.

lib-franklin.js:350 Uncaught (in promise) DOMException: Failed to execute 'add' on 'DOMTokenList': The token provided must not be empty.
at https://main--troweprice-rf--hlxsites.hlx.page/scripts/lib-franklin.js:350:55
at Array.forEach (<anonymous>)
at https://main--troweprice-rf--hlxsites.hlx.page/scripts/lib-franklin.js:350:18
at Array.forEach (<anonymous>)
at https://main--troweprice-rf--hlxsites.hlx.page/scripts/lib-franklin.js:347:25
at NodeList.forEach (<anonymous>)
at decorateSections (https://main--troweprice-rf--hlxsites.hlx.page/scripts/lib-franklin.js:326:41)
at decorateMain (https://main--troweprice-rf--hlxsites.hlx.page/scripts/scripts.js:56:3)
at loadEager (https://main--troweprice-rf--hlxsites.hlx.page/scripts/scripts.js:69:5)

Can be seen here.

Steps to Reproduce

Edit any page's section metadata, and end the style declaration with a comma (,)