- Do not allow the human to confirm a Reveal cost with 0 revealed cards if the minimum is more than zero (fixes e.g. Morph costs with "Reveal a X card" when the human player doesn't have that kind of card in hand).

forge-gui/src/main/java/forge/player/HumanCostDecision.java

@@ -855,6 +855,9 @@ public class HumanCostDecision extends CostDecisionMakerBase {
                     num = AbilityUtils.calculateAmount(source, amount, ability);
                 }
             }
+            if (hand.size() < num) {
+                return null;
+            }
             if (num == 0) {
                 return PaymentDecision.number(0);
             };