fix: `u32_sub Overflow` if the index isn't found in datastore

[khaeljy]

Pull Request type

Please add the labels corresponding to the type of changes your PR introduces:

• Bugfix

What is the current behavior?

If the index isn't found in remove_* function, then offsetted_index == 0 and panic with u32_sub Overflow in the instruction let index = offsetted_index - 1;.

What is the new behavior?

If the index isn't found in remove_* function, then offsetted_index == 0 and panic with MarketError::MARKET_NOT_FOUND.

Does this introduce a breaking change?

No

Other information

[zarboq]

Nice it will make debugging easier !