Handle checking instantiation without model answer

[PhilippImhof]

Fixes #190

[coveralls]

Pull Request Test Coverage Report for Build 14680763634

Details

• 6 of 6 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.003%) to 95.941%

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Totals
Change from base Build 14667290831:	0.003%
Covered Lines:	4018
Relevant Lines:	4188

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💛 - Coveralls