Fix TypeScript Error Preventing Build

[radamson]

When running in Docker or locally the following error occurs:

src/services/converter.service.ts:35:11 - error TS2571: Object is of type 'unknown'.

35       if (e.message.includes('ENOENT: Failed to lookup')) {
             ~

Found 1 error.

This PR adds a type assertion to fix the TypeScript error so that the build can complete.

References:

• Relevant SO post
• Relevant TypeScript GitHub Issue

[mickohanlon23]

Successfully runs in development mode and in Docker.

[nkarip]

Looks good. I can simulate the ERR_UNSUPPORTED response and get the correct 422 status.