do not double-print value when setting a repeated value

When clearning or appending to a repeated value, both the "Clearing..."
/ "Adding..." line and the "Set..." line were shown. However, this is
misleading as the only performed operation is the clearing / appending.

We fix this by directly returning from the function in case of clearing
/ appending.
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Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f