Bug/#203/pending tab crashes on load

[alfetopito]

Description

Fixed some crash scenarios for pending tab

Closes #203

To Test

1. Having a pending strategy
2. Start the app
3. Click on strategy
4. Click on pending
5. Click on the pending strategy while it's still loading

• [ ] The app should not crash

Background

More info on the bug report #203

[gnosis-info]

Travis automatic deployment:

• 🔐 Safe app link: To be added as a custom app on Safe Multisig Rinkeby, Mainnet or xDai
• 📖 Storybook: Component stories