Fix DivisionByZeroError in Responsive_Breakpoints

[aatanasov-cloudinary]

Fixing DivisionByZeroError occurring in the Responsive_Breakpoints class.

Approach

• If an attachment doesn't have width or height, the initial image tag will be rendered on the front-end without any srcset information.
• Add a debug log if there is an issue with width and height.
• Remove a debug log during syncing attachments.

QA notes

• Upload an image.
• Set its height or width to 0 (during coding, a database update was used).
• Insert the image to a page.
• Save and preview the page.
• The image should appear without errors.
• The debug log should include information about the attachment.