Throw exceptions from nested objects

[wol-soft]

Don't pass an error registry exception into a nested object and add errors to the passed exception. Instead always throw an exception from generated objects and catch those exceptions inside a parent model.

[coveralls]

Pull Request Test Coverage Report for Build 294

• 14 of 14 (100.0%) changed or added relevant lines in 6 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.003%) to 98.306%

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Totals
Change from base Build 292:	0.003%
Covered Lines:	1683
Relevant Lines:	1712

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💛 - Coveralls