[BUG] Invoke Error in platform-serverless on SQS event
### Describe the bug

After upgrading to 7.75.0, our SQS-triggered lambda using @tsed/platform-serverless is throwing invocation error:
```
{
    "errorType": "TypeError",
    "errorMessage": "Cannot convert undefined or null to object",
    "stack": [
        "TypeError: Cannot convert undefined or null to object",
        "    at Function.entries (<anonymous>)",
        "    at new entries (<trunc>/node_modules/@tsed/platform-serverless/lib/cjs/domain/ServerlessContext.js:22:48)",
        "    at Runtime.<anonymous> (<trunc>/node_modules/@tsed/platform-serverless/lib/cjs/builder/PlatformServerless.js:131:26)"
    ]
}
``` 

### To Reproduce

Create lambda with SQS trigger using serverless. 
Note that we are using custom decorator to map SQS events to ServerlessContext.

### Expected behavior

serverless-platform can bootstrap successfully

### Code snippets

_No response_

### Repository URL example

_No response_

### OS

Linux

### Node version

Node v20

### Library version

v7.75.0

### Additional context

I believe the modification in 9796c33046485aee05d1a62cec2485e3e78c38e6 made the `event.headers` as required field