java.lang.NullPointerException qsys-generate

I was successful today isolating the problem to one of my QSYS subsystems. I next started deleting components from this subsystem until there was nothing left but a memory-mapped avalon pipeline bridge, a clock bridge, and a reset bridge but nevertheless the problem remained. Next I removed all trace of the subsystem and recreated it again and now the problem is fixed.

So apparently something became corrupt in the qsys file or in one of it multitude of subordinate ip files.

It was really not time consuming to recreate the subsystem. What was time consuming was isolating to a subsystem. I found that I had to completely remove and un-wire each subsystem in-turn from platform degenerate. It was not sufficient to just un-click the use subsystem button. Furthermore each save and regenerate cycle in qsys takes a mind-numbing amount of time to complete. It also took some time to finally conclude that there was no other solution other than to delete all traces of the subsystem and start over.