[Bug] AI in fortress mode

Hello,

  So I just played a bunch of pantheon games (mostly only with AI)... and some of the were "frotress".

  The fact is that The AI players nevers buy towers upgrades.. thus their tower/fortress never heals... and so it's totaly hopeless for them to win  (skills appart...). So maybe it should be made a certain priority to the AI players to by at least the fisrt building upgrade.

Edit : After few more games I realise that the AI never buy defensive upgrade... maybe they sould do so as a good tower can be handy time to time...