[Bug] : Issue with Changing Plugins During Loading of Answers

Description:
While using Open Assistant for chat-based interactions, I encountered an issue related to changing plugins during the loading of answers. This behavior seems to result in errors and extended processing times, potentially leading to a significant problem for users.

Steps to Reproduce:

1. Begin a chat session with Open Assistant.
2. Pose an irrelevant question, such as "What is giggity giggity?"
3. While the chatbot is processing the question, attempt to change the plugin being used.
4. Observe that this action leads to an error in the answer generated by the chatbot.
5. In some cases, the chatbot may produce a response containing repeated question marks (??????????????????????????????????...), entering an infinite loop of such characters.

Expected Behavior:
The expected behavior is that users should not be able to change plugins while the chatbot is in the process of answering a question. The plugin selection should be disabled during this loading period. Once the answer has been generated and presented to the user, they should then have the ability to change the plugin for subsequent interactions.

Impact:
The current behavior can lead to frustration for users, as it generates errors and extended processing times. Users may encounter unexpected and unintelligible responses, causing confusion and a less-than-ideal experience with Open Assistant.

Proposed Solution:
Implement a feature that temporarily disables the option to change plugins while the chatbot is actively processing a question. Once the answer is ready, re-enable the plugin selection for users to switch if desired.

Additional Notes:
This bug has the potential to impact user engagement and satisfaction with Open Assistant. As the project aims to provide access to a high-quality language model, addressing this issue would significantly enhance the overall user experience and reliability of the platform.

The issue does not name files or tests. Start by reproducing the chat flow while an answer is loading, then trace the plugin selector and loading state in the chat interface. Done means plugin changes are unavailable during generation, become available afterward, and the error or repeated-question-mark response no longer occurs.