fix(usb): 解决USB设备权限拒绝时的空指针异常

- 添加了对null设备对象的检查
- 为空设备提供了合适的错误日志信息
- 防止了潜在的崩溃问题

android/src/main/java/com/xiarui/zhiwen/UsbController.java

@@ -424,7 +424,11 @@ public class UsbController {
             new IPermissionListener() {
                 @Override
                 public void onPermissionDenied(UsbDevice d) {
-                    l("Permission denied on " + d.getDeviceId());
+                    if (d != null) {
+                        l("Permission denied on " + d.getDeviceId());
+                    } else {
+                        l("Permission denied (device unavailable)");
+                    }
                 }
             });