Malaria: relatively small "Vector_Migration_Food_Modifier" can cause floating point crash

[stitova-idm]

Was trying to make vectors really hungry and changed "Vector_Migration_Food_Modifier": 100,
this causes floating point issue when the modification is exponential because we use:
fm = exp( sp * m_ModifierFood * pr ) - 1.0f; formula and sp and pr are often likely to be 1;

I think we need to limit Vector_Migration_Food_Modifier food size when using ModiferEquationType::EXPONENTIAL