fatching the value of data from database but there is no value is present for data so return null value from DB ...want to check that value & proceed

$search_med_shape_2="select fs.shape_date,fs.shape_category,fd.next_review_date 
                     from force_shape_2 fs,force_shape_2_detail fd  
                     where fs.force_id='".$fid."'
                        and fs.force_id=fd.force_id and fd.next_review_date<>'1970-01-01 00:00:00'
                     order by shape_date desc limit 1";
$s_med_shape_2=mysqli_query($connpis,$search_med_shape_2);
$s_m_shape_2=mysqli_fetch_array($s_med_shape_2,MYSQLI_ASSOC);
$med_shape_1=mysqli_num_rows($s_m_cat);
$med_shape_2=mysqli_num_rows($s_med_shape_2);
if($s_m_shape_2['next_review_date'] == "") // line no 362 where error is showing
{
    $s_m_shape_2['next_review_date'] = '0';
}
if($med_shape_1>'0' or $med_shape_2>'0')
{
							
    if($s_med_cat['shape_date']>$s_m_shape_2['next_review_date'])
    {
								
        $ind_med_shape=$s_med_cat['code']." As On ";
        $ind_med_shape_date=date("d-m-Y",strtotime($s_med_cat['shape_date']));
    }

error showing is:
>Trying to access array offset on value of type null in /home/FTP/e_sangrahan/DataSearch/new_policy/personsdetails_new_policy.php on line 362

line no 362 is commented above...

As @barmar suggested, the most plausible explanation for the error at line 362 is that the query produces no results.

The condition that could most likely fail is: WHERE fs.force_id='".$fid."': I assume that there is no row with force_id equal to the value contained in the variable $fid. I advise you to inspect the value of $fid (for example with var_dump) before passing it to the query.
Furthermore, the composition of the query with a concatenation of strings exposes to a possible SQL injection, it would be better to use with prepared statements

This could be an improvement of your code:

// query with joins
$sql_med_shape_2 = <<<SQL 
	SELECT fs.shape_date, fs.shape_category, fd.next_review_date 
    FROM force_shape_2 fs
    INNER JOIN force_shape_2_detail fd ON fs.force_id = fd.force_id  
    WHERE fs.force_id = ? 
	  AND fd.next_review_date <> '1970-01-01 00:00:00'
    ORDER BY shape_date DESC
    LIMIT 1
SQL;	

// ----- debug $fid content
// echo '<pre>
// var_dump ($fid);
// die

// prepared statement
$stmt_med_shape_2 = mysqli_stmt_init($connpis);
mysqli_stmt_prepare($stmt_med_shape_2, $sql_med_shape_2);
mysqli_stmt_bind_param($stmt_med_shape_2, 's', $fid);
mysqli_stmt_execute($stmt_med_shape_2);
$result_med_shape_2 = mysqli_stmt_get_result($stmt_med_shape_2);
$s_m_shape_2 = mysqli_fetch_array($result_med_shape_2, MYSQLI_ASSOC);

$med_shape_2 = mysqli_num_rows($result_med_shape_2);

// let's test BEFORE if we have any result row
if ($med_shape_2 > 0) {
	
	$s_m_shape_2['next_review_date'] = $s_m_shape_2['next_review_date'] ?: 0;  // 'previous' line no 362
	
	//....