Do not show img tag with same src attribute if an image field is empty

[PedroErnst]

This PR fixes a small bug with the image type field from Studio / Module Builder.

Description

Image fields have in their src attribute the url of an entrypoint composed of the id of the record we're viewing and the name of the field. However, once we clear an image field, since this url doesn't change the browser might display a cached version where we would expect not to see any image.

How To Test This

1. Add an image field to any module
2. Add it to detail and edit view
3. Edit a record, upload an image to this field
4. See it displays in detail view
5. Edit the record, remove the image
6. See it doesn't display in detail view. The img tag should have an empty src attribute.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Final checklist

• My code follows the code style of this project found here.
• My change requires a change to the documentation.
• I have read the How to Contribute guidelines.

[Dillon-Brown]

Assessed