Bug updating snippet without repository

What does this MR do?

In this MR we address three things:

• We move the commit action outside the db transaction because this generated a race condition. More info in #213436 (closed)
• We remove the snippet repository when there is an error and it is empty
• We roll back the changes made in !28516 (merged) because there are some exceptions that reveals too much information.

Closes #213436 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content