Fix #1320: Do not print an error when analysing a lambda function and its associated execution role was previously deleted.

[Tzaoh]

Description

Currently, when analysing a lambda function but its associated role execution does not exist, ScoutSuite triggers a NoSuchEntityException exception, printing an error line.

The current change set a condition to check this use case and not printing the corresponding error.

Fixes #1320

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

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
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works (optional)
• New and existing unit tests pass locally with my changes