Add test coverage for processFirstBuddy function

[coderabbitai[bot]]

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The function processFirstBuddy in packages/nps/gameMessageProcessors/processGetFirstBuddy.ts lacks test coverage. This is crucial for ensuring its reliability and correctness. Please refer to the following PR and comment for more details:\n\nPR URL: https://github.com/rustymotors/server/pull/2037\nComment URL: https://github.com/rustymotors/server/pull/2037#discussion_r1724152002