State becomes uneditable through Admin API when set to ⁠undefined in TypeScript SDK

[nikrooz]

I encountered an issue where setting a state to ⁠undefined (via TS SDK) causes the state to become uneditable through the Admin API.

await ctx.set("undefined", undefined);

The SDK does not raise any errors or warnings when setting the state to ⁠undefined, but this leads to unexpected behaviour where the state cannot be modified via the Admin API anymore.