Fix type of dividing by GenericAffExpr with no terms

[odow]

Replacement for #4262

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.95%. Comparing base (00f9391) to head (c0543c1).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4263   +/-   ##
=======================================
  Coverage   99.95%   99.95%           
=======================================
  Files          43       43           
  Lines        6333     6346   +13     
=======================================
+ Hits         6330     6343   +13     
  Misses          3        3           

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[blegat]

This is maybe a bit inconsistent with other operations. For instance, when we multiply two affine expression together, we always create a quadratic one, we don't check whether one of them is a constant. So I feel it should be the same here, we should always create a nonlinear one and the user can convert it to constant if needed.

[odow]

Closing because, on reflection, I agree with @blegat.

@acostarelli you should change your code to not divide by an AffExpr.