Function getReportCollection returns null with HTTP error 500

[rmalaha]

I have created a custom SQL special report trough Reports -> Special Reports -> Add Report. After creating "Orders overview" and i go to Reports -> Special Reports -> Orders overview i can see the results fetched from the DB.

The problem comes when i click on export to create an CSV or Excel it gives me a HTTP 500 error. I have also increased my .htaccess file memory_limit 1024M and max_execution_time 18000. The overview fetches only 12 records so i don't think it has to do with memory limitation.

When looking trough the error.log of ngix i get the following, i could not figure out what this exactly mean. Nothing specific trough Google search either.

The server error.log returns the following error:
2018/06/19 14:11:35 [error] 5238#5238: *735 FastCGI sent in stderr: "PHP message: PHP Fatal error: Uncaught Error: Call to a member function getReportCollection() on null in /var/www/dev/.modman/kalenjordan_custom-reports/app/code/community/Clean/SqlReports/Block/Adminhtml/Customreport/View/Grid.php:38
Stack trace:
#0 /var/www/dev/.modman/kalenjordan_custom-reports/app/code/community/Clean/SqlReports/Block/Adminhtml/Customreport/View/Grid.php(77): Clean_SqlReports_Block_Adminhtml_Customreport_View_Grid->_createCollection()

Not sure where to look or how to fix this issue. If someone might understand what this means or where i should look, please let me know.

Roy