Minor fix: GET method on non existing shovel crash

[SimonUnge]

Proposed Changes

GET on non-existing shovel caused internal error.

Types of Changes

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• Bug fix (non-breaking change which fixes issue Shovel HTTP API: GET /api/shovels/vhost/{vhost}/{name} returns 500 error for names that do not exist #12168)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause an observable behavior change in existing systems)
• Documentation improvements (corrections, new content, etc)
• Cosmetic change (whitespace, formatting, etc)
• Build system and/or CI

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Further Comments

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