[sglang] fix: fix missing engine_kwargs

[vermouth1992]

What does this PR do?

• fix missing engine_kwargs that causes CI on main to fail

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[gemini-code-assist]

Code Review

This pull request fixes a potential crash when engine_kwargs is missing in the SGLang rollout configuration. The review suggests handling a null value for engine_kwargs and improving variable naming for clarity.

[gemini-code-assist]

To improve robustness, handle the case where self.config.get("engine_kwargs") returns None[^1]. Also, for clarity, rename engine_kwargs to sglang_kwargs to reflect that it holds the sglang-specific kwargs.

Suggested change

	engine_kwargs = self.config.get("engine_kwargs", {}).get("sglang", {})
	attention_backend = engine_kwargs.get('attention_backend', None)
	engine_kwargs = self.config.get("engine_kwargs")
	sglang_kwargs = engine_kwargs.get("sglang", {}) if engine_kwargs else {}
	attention_backend = sglang_kwargs.get('attention_backend', None)