i have the following array:
$keyvisual_data = array(
\'video_file\' => $row->field_field_video[0][\'rendered\'][\'#item\'][\'uri\'],
You could add a shorthand check if each value is null
$default_value = "Default value";
$keyvisual_data = array(
'video_file' => ($row->field_field_video[0]['rendered']['#item']['uri'] == null) ? $default_value : $row->field_field_video[0]['rendered']['#item']['uri']
// etc.. etc...
);
A less messy version of this, to explain the code more clearly:
($video_file == null) ? $default_value : $video_file
);
// Will output "I am a Default value"
echo $new_array['video_file'];
?>