More effectmod parser work.

src/engine/ConfigParsing/EffectsParser.java

@@ -190,7 +190,11 @@ public class EffectsParser {
                 case ImmuneTo:
                 case BlackMantle:
                     effectModifier.arg1 = modValues.get(1).trim();
-                    effectModifier.arg2 = modValues.get(2).trim();
+
+                    // Some BlockedPowerType entries have only one argument
+
+                    if (modValues.size() > 2)
+                        effectModifier.arg2 = modValues.get(2).trim();
                     break;
                 case NoMod:
                 case ConstrainedAmbidexterity: