Mysqli fetch array from stored prepared statement resulted in an error

Question

I am working on a user registration page. I want to check if the username or email exist before an account is created. I saved the stored query from the prepared statement into the variable "$result" using mysqli_stmt_get_result and tried to fetch the result using mysqli_fetch_array, but I got an error that read;

Warning: mysqli_fetch_array() expects parameter 1 to be mysqli_result, bool given in localhost

The codes below resulted in "result empty". This is the main issue.

$result = mysqli_stmt_get_result($stmt);
if($result) {
    while ($row = mysqli_fetch_array($result, MYSQLI_ASSOC)) {                 
        if($row['username']==$username && $row['email']==$useremail){
            header("Location: ../register.php?error=error&usernametaken&emailexist");
            exit();
        }
        elseif($row['username']==$username){
            header("Location: ../register.php?error=error&usernametaken");
            exit();
        }
        elseif($row['email']==$useremail){
            header("Location: ../register.php?error=error&emailexist");
            exit();
        }
    }
} else {
    echo "result is empty";

}

Below is the full code

$sql = "SELECT username, email FROM users WHERE username = ? OR email = ?";
$stmt = mysqli_stmt_init($conn);
if(!mysqli_stmt_prepare($stmt, $sql)) {
    header("Location: ../register.php?error=sqlerror");
    exit();
}
else {
    mysqli_stmt_bind_param($stmt, "ss", $username, $useremail); 
    mysqli_stmt_execute($stmt);

    //check if the username exist
    mysqli_stmt_store_result($stmt);
    $rowCount = mysqli_stmt_num_rows($stmt);    
    $result = mysqli_stmt_get_result($stmt);
    
    if($rowCount > 0) {
        if($result) {
            while ($row = mysqli_fetch_array($result, MYSQLI_ASSOC)) {                 
                if($row['username']==$username && $row['email']==$useremail){
                    header("Location: ../register.php?error=error&usernametaken&emailexist");
                    exit();
                }
                elseif($row['username']==$username){
                    header("Location: ../register.php?error=error&usernametaken");
                    exit();
                }
                elseif($row['email']==$useremail){
                    header("Location: ../register.php?error=error&emailexist");
                    exit();
                }
            }
        } else {
            echo "result is empty";

        }               
    } else {
        $sql = "INSERT INTO users (username, email, name, password) VALUES (?, ?, ?, ?)";
        $stmt = mysqli_stmt_init($conn); 
        if(!mysqli_stmt_prepare($stmt, $sql)) { 
            header("Location: ../register.php?error=sqlerror");
            exit();
        } else {     
            $hashedPass = password_hash($password, PASSWORD_DEFAULT);     
            mysqli_stmt_bind_param($stmt, "ssss", $username, $useremail, $first_name, $hashedPass); 
            mysqli_stmt_execute($stmt);
            header("Location: ../register.php?success&registered");
        }
    }

}
mysqli_stmt_close($stmt);
mysqli_close($conn); 

I am running it on a local server though. I humbly await your input.