[Kinetics] Ensure that equilibrium constants are not zero
[Kinetics] Ensure that equilibrium constants are not zero

This prevents reverse rate constants from becoming NaN when the forward rate
constant underflows.

git-svn-id: e76dbe14710aecee1ad27675521492cea2578c83@2157 02a645c2-efd0-11dd-984d-ab748d24aa7e

Cantera/cantera-svn,Cantera/cantera-svn,Cantera/cantera-svn,Cantera/cantera-svn,Cantera/cantera-svn,Cantera/cantera-svn