PBX Manager module error

[phongkni]

When I enter the PBX Manager module and then select a filter I get the error message.

   

Then I opened the PBX Manager module again and got the following error

Fatal error: Call to a member function sql_escape_string() on null in C:\xampp\htdocs\data\CRMEntity.php on line 3507


How to fix this problem. Thanks