Describe the bug

If a trigger defines a payload with a source value that is null, the JSON that is passed as the trigger payload is an invalid JSON.

To Reproduce

1. Define trigger with payload a follows:

payload:
- dest: nullable_key
   src:
     useRawData: true
     dataKey: body.nullable_key

2. Receive event from source with JSON as { ... "nullable_key": null, ... }.
3. The payload JSON object received by trigger is { ... "nullable_key": , ... }, which is invalid JSON.

Expected behavior

The payload should be { ... "nullable_key": null, ... }.

Environment (please complete the following information):

• Argo Events: 1.9.7
• Tested with Kafka Trigger and Custom Trigger.

Message from the maintainers:

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