[Couenne] Assertion failed in BonChooseVariable

[Giacomo Nannicini]

Hi,
in Couenne trunk, there is an assertion that sometimes fails when
branching with CouenneChooseStrong:

couenne: ../../../../../Bonmin/src/Algorithms/Branching/BonChooseVariable.cpp:969:
virtual void Bonmin::BonChooseVariable::updateInformation(const
OsiBranchingInformation*, int, OsiHotInfo*): Assertion
`object->upEstimate()>0.0&&object->downEstimate()>0.0' failed

I couldn't find out why this happens but it may be worth having a
look: the values object->upEstimate() and object->downEstimate()
appear in some denominators later on, so, this could cause some
Infinity/NaN, hence troubles. I'll let you know if I discover the
source.

Giacomo