This fixes a problem with error handling when using the file locking logic, and adds a no_source.bed example where the source graph it not available, and so the left and right buttons don't work.
It also revises the BED lines generated by the chunk extraction script to refer to the coordinates used for the extraction, and not the actual extracted coordinates, so it matches better with the non-pre-extracted behavior.
This fixes a problem with error handling when using the file locking logic, and adds a
no_source.bedexample where the source graph it not available, and so the left and right buttons don't work.It also revises the BED lines generated by the chunk extraction script to refer to the coordinates used for the extraction, and not the actual extracted coordinates, so it matches better with the non-pre-extracted behavior.