Fix IndexOutOfBoundsException for fake brew event by adding to list instead of setting the index (which doesn't work) (#4655)

src/main/java/com/gmail/nossr50/skills/alchemy/AlchemyPotionBrewer.java

@@ -129,7 +129,7 @@ public final class AlchemyPotionBrewer {
             inputList.add(input);
 
             if (output != null) {
-                outputList.set(i, output.toItemStack(item.getAmount()).clone());
+                outputList.add(output.toItemStack(item.getAmount()).clone());
             }
         }