1. lyx-code 2. enter aaaaa 123456 (there are four leading spaces) 3. change environment to standard 4. select aaaaa and 1 5. cutaaaaa, 12345 are removed. It is pretty easy to avoid the crash by adding something like right = min(right, par[pit].size() + 1) after line 304 of CutAndPaste.cpp, but I believe that a better treatment is required.
Isn't every crash a critical bug? Why nobody is interested? Bo