Fix staking storybook js error related to "theme"

[nevendyulgerov]

Which network is that happening?

Mainnet

Which Explorer is that Bug happening?

Staking

🙂 Expected behavior

Storybooks should be displayed when you open the staking storybook app.

🫠 Actual behavior

Storybooks aren't displayed when you open the staking storybook app. Instead, a js error appears related to "theme":

🧪 Minimal test case

1. Run the staking storybook with yarn storybook
2. Open the storybook app
3. Open any component

📄 Extra information

No response