There seems to be some models not handling correctly the non-nullability of toolCallArguments when defining a tool call. For example, the Ollama implementation is always null-safe (if no tool argument, then '{}' is used). Other implementations might produce a null value.
This PR relaxes the toolCallArguments validation to support null toolCallArguments within ToolCallingObservationContext.
Fixes gh-3234
Signed-off-by: Thomas Vitale <ThomasVitale@users.noreply.github.com>