Json error while migrating

[obuisard]

During migration, error:

<br/>
<b>Warning</b>
:  Undefined array key "post_title" in <b>E:\bearsampp\www\testfresh_5_2_2\plugins\migratetojoomla\wordpress\src\Extension\Wordpress.php</b>
on line <b>745</b>
Error is: 
<br/>
<br/>
<b>Deprecated</b>
:  strtolower(): Passing null to parameter #1 ($string) of type string is deprecated in <b>E:\bearsampp\www\testfresh_5_2_2\plugins\migratetojoomla\wordpress\src\Extension\Wordpress.php</b>
on line <b>780</b>
<br/>
<br/>
<b>Deprecated</b>
:  strtolower(): Passing null to parameter #1 ($string) of type string is deprecated in <b>E:\bearsampp\www\testfresh_5_2_2\plugins\migratetojoomla\wordpress\src\Extension\Wordpress.php</b>
on line <b>782</b>
<br/>[[],{"status":"error"}]