Smart Contracts: Make the 'condition inherit' block mandatory

[bchamagne]

Description

The condition inherit always were mandatory, but there was a bug in the code.
This resulted in the ability to create smart contracts without the block but the contracts were unable to produce any next_tx because they would all fail the inherit constraints. (empty condition inherit block ==> refusing all transactions).

ps: the condition inherit block will become optional in a later release.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Manual test

• Unit test added

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules