Trying to access array offset on value of type null

$file_show = mysqli_query($link,$file_show) or die('Query failed:'. mysqli_error());$file_row=mysqli_fetch_array($file_show);echo $file_row[0];$print_name = $target_row[2];if($file_row[0] == "ntof"){  $treechange = 1;  $upnodename = $file_row[2];}else{  $treechange = 0;  $upnodename = $target_row[2];}
isset($cOTLdata['char_data'])
$len = isset($cOTLdata['char_data']) ? count($cOTLdata['char_data']) : 0;
if(isset($file_row[0])){if($file_row[0] == "ntof"){$treechange = 1;$upnodename = $file_row[2];}else{$treechange = 0;$upnodename = $target_row[2];}}

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