Better error handling - switching between networks in confirm swap modal

[MareenG]

Description When switching between networks while already the confirm swap modal is open there is no proper error message

How to Reproduce Steps to reproduce the behavior:

1. Go to cowswap
2. Place a swap
3. Click on swap
4. Instead of confirm swap change network

Expected behavior An error message should appear Best case the desired swap remains( input token and sell/buy amount) and is adjusted to the new network

Screenshots https://user-images.githubusercontent.com/34510341/134506627-b3a1af89-fc5a-44b6-8ba1-a8c3b1ecdeee.mov

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. If you think it shouldn't be closed, speak now or forever hold your peace.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. If you think it shouldn't be closed, speak now or forever hold your peace.