Database inconstistency in nG6

Problem: 673 links project/run while the run doesn't exist anymore. The most recent run in this series was made Monday 3 April 2017 22:00:00. (This error impacts at least the migration process.)

SELECT * FROM tx_nG6_project_run WHERE run_id NOT IN (SELECT uid FROM tx_nG6_run)

Tests: Deleting the run via the web interface also deletes the link. So the inconstistency doesn't come from here.

To do:

• Remove the obsolete links
• Test if the purge process is responsible. (It shouldn't delete the run nor the link.)
• Update the database structure to add an integrity constaint.
• Check if the analyzes have the same problem (project/analyze, run/analyze, analyze/result).