There have been changes to the driver in the Master branch, one of which was to remove that "assert" and thus handle an error more elegantly.
github.com/LinuxCNC/linuxcnc/commit/6024...7aa599ef908L465-L542
Not directly helpful, but does seem to suggest you may not be the only one who had that problem.
If you are able to build from source, you could make that change and recompile? (Or start running 2.10)