Fix crash when attempting to render Gutenberg comment

[itsmeichigo]

Fixes woocommerce/woocommerce-ios#11770
Reported in peaMlT-p5-p2

Description

There's a recent crash found in Woo iOS happening in CommentAttachmentRenderer when attempting to render an image with an illegal size (-1, -1).

This PR fixes this crash with two steps:

• Added a guard check to ensure the image size is acceptable before sending it to UIGraphicsBeginImageContextWithOptions
• Move the guard check for Gutenberge comment on the top before proceeding to render an image.

Testing steps

When trying to reproduce the crash, I found that this happens when a product description in Woo contains some Gutenberg comments. I added similar comments to the Example/Example/SampleContent/content.html file, so you can test with the example app by tapping Standard demo and confirm that the app doesn't crash.

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• I have considered if this change warrants release notes and have added them to the appropriate section in the CHANGELOG.md if necessary.

[hafizrahman]

Nice fix! Great that you add the size check too.

I also was able to replicate the crash by testing the content.html change here with trunk build, perfectly matches the Sentry report trace in woocommerce/woocommerce-ios#11770:

LGTM 👍🏼