Nullpointer when handling a null body in webhook response

[sbuettner]

Describe the Bug

When using an incomplete response expression without a body:

  "status": 200
}

It leads to a NullpointerException in the runtime during the escape routine at

connectors/connector-runtime/connector-runtime-spring/src/main/java/io/camunda/connector/runtime/inbound/webhook/InboundWebhookRestController.java

Line 88 in ed511b2

if (Objects.requireNonNull(value) instanceof String s) {

Steps to Reproduce

Create a webhook connector and use the following response expression:

```{
  "status": 200
}

It will lead to a NullpointerException.

Expected Behavior

It should not lead to a nullpointer exception.

Environment

• Connector Runtime 8.6.2