Explain Code: Do not show "empty-state" when loading

What does this MR do and why?

The GitLab Chat: Adding empty state (!121703 - merged) introduced the empty state to GitLab chat. The condition to render this state had to be fine-tuned for the Explain Code feature to not show it when the request is being sent out already (isLoading: true state). This MR fixed it.

Screenshots or screen recordings

	Before	After
GitLab chat	empty-state-gitlab-chat-before	empty-state-chat-after
Explain Code	empty-state-ec-before	empty-state-ec-after

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