fix: improve state handling and JSON parsing with better error handling

[ManojINaik]

No description provided.

[warmshao]

Hi, I am Ok with the part of parsing json, which seems to be more robust. But:

1. Regarding state = await self.browser_context.get_state(use_vision=self.use_vision) and handling browser_state: Why is this change necessary here? What specific problem does it solve, or what enhancement does it provide? Additionally, if a change is indeed required, it shouldn't be implemented directly within get_state. This negatively impacts code maintainability.
   For both of these points, I recommend providing a clear explanation and comparative tests demonstrating the problem being addressed. If these changes are confirmed to be more robust, the updates should be synchronized with the official browser-use component rather than being implemented solely within the web-ui.

2. Regarding getattr for step_info. There are some unnecessary changes. For instance, using getattr to access step_info seems redundant as it already has an initial value.

3. Please try to make each PR address a single feature or optimization. This will make the review process much easier. Let's refactor this current PR to focus only on optimizing the JSON parsing.

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