Getting Error : Error: No modules found when analyzing null. in Qsys -> synthesis (under component editor)

It looks like you're using an older version of Quartus (tool labeled Qsys instead of Platform Designer). Unfortunately, in some of those older versions, if there was any error in your code, that error message would be all the Component Editor would display, which is pretty useless for debugging (basically, it was a bug in the Component Editor).

You could either post the code here for others to take a look at or synthesize the code directly in Quartus instead of through the Component Editor. Quartus will provide detailed messages on any issues with the code. Once you've fixed the issues, you can then take it back through the Component Editor to continue building your component.

Or you could install a newer version of Quartus where the issue is fixed.

#iwork4intel

For your information, the latest release of Quartus would be Q19.1std for linux or Q18.1windows.

This should an know issue as well

https://www.intel.com/content/www/us/en/programmable/support/support-resources/knowledge-base/tools/2017/error--no-modules-found-when-analyzing-null.html