Empty metadata --> tool tag causes parsing exception

Hello, I have a question regarding an exception I get when parsing a 1.3 CycloneDX SBOM.

According to the specification, the `` tag in the `` section is an `array`, which does not specify a constraint to it's size: https://cyclonedx.org/docs/1.3/json/#metadata_tools

However, when I try to parse an SBOM like this using your library:

```xml

```

I get this exception:

```
com.fasterxml.jackson.databind.JsonMappingException: Cannot coerce empty String ("") to `org.cyclonedx.model.Tool` value (but could if coercion was enabled using `CoercionConfig`)
at [Source: UNKNOWN; byte offset: #UNKNOWN] (through reference chain: org.cyclonedx.model.Bom["metadata"])
```

The SBOM is generated using a tool, but it does not fill out this property.
I was wondering whether this behavior is intended or whether this is a difference to the specification that I did not understand.

Thank you for your time.

Reproduce the exception with the CycloneDX 1.3 XML shown, then trace deserialization through org.cyclonedx.model.Bom metadata and org.cyclonedx.model.Tool. Confirm whether an empty tools element is accepted by the specification, and consider the issue complete when that input is handled consistently without the reported parsing exception.

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