Fix "Attempt to get java.util.List field 'PacketOpcodes.BANNED_PACKETS' with...

Fix "Attempt to get java.util.List field 'PacketOpcodes.BANNED_PACKETS' with illegal data type conversion to int"

src/main/java/emu/grasscutter/net/packet/PacketOpcodesUtil.java

@@ -17,6 +17,7 @@ public class PacketOpcodesUtil {
 		Field[] fields = PacketOpcodes.class.getFields();
 
 		for (Field f : fields) {
+			if(f.getType().equals(int.class)) {
 				try {
 					opcodeMap.put(f.getInt(null), f.getName());
 				} catch (Exception e) {
@@ -24,6 +25,7 @@ public class PacketOpcodesUtil {
 				}
 			}
 		}
+	}
 
 	public static String getOpcodeName(int opcode) {
 		if (opcode <= 0) return "UNKNOWN";