There is a  processor that runs every night, when  the processor ran it encountered with a null value and hence the error  logged. When it has a program area like this (a number 7079...), that means it's from an Apex Job.

You may see some more descriptions in the setup > monitor > apex  jobs.  Look for something that ran at the same date/time the error log  was created.  That would at least give the Apex Batch Processor name  that caused the issue. Please check if you have updated latest release note version.