Set activating player when evaluating mana producing permanent by AI, to avoid warnings being printed.

forge-ai/src/main/java/forge/ai/ComputerUtilMana.java

@@ -88,6 +88,7 @@ public class ComputerUtilMana {
             score = 0;
 
             for (SpellAbility ability : card.getSpellAbilities()) {
+                ability.setActivatingPlayer(card.getController());
                 if (ability.isManaAbility()) {
                     if (ability.getManaPart() == null) {
                         score++; //Assume a mana ability can generate at least 1 mana if the amount of mana can't be determined now.