[BRLTTY] brl.cursor and electric fence error report

[Jason White]

The following occurred during normal operation of BRLTTY under electric fence
as part of my testing process.


Core was generated by `/bin/brltty'.
Program terminated with signal 11, Segmentation fault.
#0  0x0000000000410ac6 in main (argc=1, argv=0x7fff9ccc9908) at ./main.c:2485
2485                brl.buffer[brl.cursor] |= cursorDots();

Note also that brl.cursor = 40 and that the display has 40 cells.

Does this look like a potential off-by-one bug?

It took quite a while to trigger this one.