Fix serverbound beacon secondary effect

Author: kennytv

common/src/main/java/com/viaversion/viabackwards/protocol/protocol1_20to1_20_2/rewriter/BlockItemPacketRewriter1_20_2.java

@@ -112,8 +112,11 @@ public void registerPackets() {
         });
 
         protocol.registerServerbound(ServerboundPackets1_19_4.SET_BEACON_EFFECT, wrapper -> {
-            if (wrapper.passthrough(Type.BOOLEAN)) {
-                // Effects start at 1 before 1.20.2
+            // Effects start at 1 before 1.20.2
+            if (wrapper.passthrough(Type.BOOLEAN)) { // Primary effect
+                wrapper.write(Type.VAR_INT, wrapper.read(Type.VAR_INT) - 1);
+            }
+            if (wrapper.passthrough(Type.BOOLEAN)) { // Secondary effect
                 wrapper.write(Type.VAR_INT, wrapper.read(Type.VAR_INT) - 1);
             }
         });