我收到此错误
警告：试图访问第15行E：\xampp\htdocs\word-meaning-learn\word-ajax-insert.php中类型为null的值的数组偏移量插入了含义数据！
行上的代码有什么问题？〉if($row['bangla_mean'] == $bangla_mean)

<?php
include "config.php";
$bangla_mean = $_POST["bangla_mean"];
$english_mean = $_POST["english_mean"];
$example_mean = $_POST["example_mean"];
$synonym_mean = $_POST["synonym_mean"];

if(isset($bangla_mean)){
  $stmt = $conn->prepare("SELECT bangla_mean FROM wordmeanings_table WHERE bangla_mean=?");
$stmt->bind_param("s",$bangla_mean);
$stmt->execute();
$result = $stmt->get_result();
$row = $result->fetch_array(MYSQLI_ASSOC);

if($row['bangla_mean'] == $bangla_mean){
  $response = "This Bangla meaning already exist!";
  }
 else{
  $stmt = $conn->prepare("INSERT INTO wordmeanings_table (bangla_mean, english_mean, example_mean, synonym_mean) VALUES (?, ?, ?, ?)");
        $stmt->bind_param("ssss",$bangla_mean,$english_mean,$example_mean,$synonym_mean);
      if($stmt->execute()){
        $response = "Inserted the meaning data!";
      }
      else{
        $response = "Something went wrong!";
      }
  }
}

echo $response;
        exit;
?>