title: Return null from fun in kotlin
body: <p>I've written a function to perform a database query. I want it to return <code>null</code> if it cannot fetch any result.</p>
  
  <pre><code>fun getServiceCharge(model: String): ServiceChargeMasterList {
      val unique = VideoconApplication.daoSession.serviceChargeMasterListDao.queryBuilder().where(ServiceChargeMasterListDao.Properties.ModelCategory.eq(model)).unique()
      if (unique != null)
          return unique
      else
          return null!!
  }
  </code></pre>
  
  <p>It gives me <strong><code>kotlin.KotlinNullPointerException</code></strong>.</p>
  
  <p>Can anyone tell me how can I solve this?</p>