Fix needsModel method for CEGQI (#5048)

Fix needsModel method for CEGQI (#5048)

There was a bug in CEGQI's needModel method which could say that it doesnt need a model built when there are no active quantifiers. However, computing active quantifiers is not done in QuantifiersEngine::check until after this method is called, meaning it was using stale data on whether a quantifier was active or not. This could lead to the use of bogus models in CEGQI in incremental mode in some corner cases, leading to the assertion failure in #5019.

Fixes #5019.