Improve safety of IFEQ/IFNE check in OpaquePredicateTransformer

deob/src/main/java/dev/openrs2/deob/transform/OpaquePredicateTransformer.kt

@@ -88,14 +88,18 @@ class OpaquePredicateTransformer : Transformer() {
         // find and fix opaque predicates
         for (match in OPAQUE_PREDICATE_MATCHER.match(method).filter { isOpaquePredicate(method, it) }) {
             val branch = match[1] as JumpInsnNode
-            if (branch.opcode == Opcodes.IFEQ) {
+            when (branch.opcode) {
+                Opcodes.IFEQ -> {
                     // branch is always taken
                     method.instructions.remove(match[0])
                     branch.opcode = Opcodes.GOTO
-            } else { // IFNE
+                }
+                Opcodes.IFNE -> {
                     // branch is never taken
                     match.forEach(method.instructions::remove)
                 }
+                else -> error("Invalid opcode")
+            }
 
             opaquePredicates++
         }