Describe the bug
Seems like base64 encoded images do not work when using the mistral ai connector in C#.
When i try to add an image from a stream i get an exception when sending the message to mistral.
I think its releated to this line:
https://github.com/microsoft/semantic-kernel/blob/88635e177a1175357d3bcc990127a43b18d6106d/dotnet/src/Connectors/Connectors.MistralAI/Client/MistralClient.cs#L787C1-L794C14

This is the way i create the image content to be added:

using var imageContentStream = await GetImageContentMemoryStreamAsync(content);

return new ImageContent(imageContentStream.ToArray(), MimeTypes.GetMimeType(content.FileName));
As is see the Uri Property of the ImageContent is not set then.

Platform

• OS: Windows
• IDE: Visual Studio
• Language: C#, Python
• Source: latest nuget version

Additional context
I already posted this inside this issuce #9844.