Fix issue related to sanity checking integer models (#7363)

Fix issue related to sanity checking integer models (#7363)

We now insist that we sanity check integer models in linear logics. Previously, we could trigger an assertion failure in Minisat if a user asked for a model in a state where the linear solver had assigned a real value to an integer variable, as we would be sending a lemma during collectModelValues in a state where we had already terminated with "sat".

This also changes an assertion to warning, to allow the regression to pass.

Fixes #6774 (This PR fixes a followup issue after the original bad model reported there was fixed by sanity checks).

As the assertion failure is downgraded to a warning, fixes #6988, fixes #7252.