Fixed pointless exception in logs every time a category with image is saved

[woutersamaey]

Fixed a pointless exception in the logs every time a category is saved that has an image, even when nothing was changed.
When no image is uploaded, there is no need to try to process it.

Currently there is a try catch which writes an error to the log, but this is also triggered when no image is changed or uploaded. The log thus contains errors that aren't problematic.

Description

Fixed superflous exception from logs every time a category (with image) is saved, even when no changes were made to the category,

Fixed Issues (if relevant)

1. Fixed a superflous error message from getting in the logs. This alarms the developer/shopkeeper when there is actually no problem at all.

Manual testing scenarios

1. Save a category that has an image. No need to change anything really.
2. The exception log should not contain a "critical" exception about a problem writing the file.

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[okorshenko]

HI @woutersamaey
Thank you for your fix. Could you please fix broken tests so that we can proceed with Pull Requests acceptance?

Thank you

[Ctucker9233]

@magento-team What version of 2.2 will have this fix? It's not in 2.2.7.