Handle disassembly buffer

[bogdan-nikitin]

Fix #956 (comment)

The disassembly buffer is of the "nofile" type, which has not been handled. This leads to the error "cursor position outside the buffer" when more than two panes opened.

This error can be reproduced using this Dockerfile:

1. Run container interactively. Neovim opens with an example file with a breakpoint set
2. Type :DapContinue
3. Type :DapStepInto few times
4. Assembly will appear in both panes

[mfussenegger]

Thanks for the PR but this fix would have the side effect that if you're stepping from any other window with a nofile buffer (like variables window) it would switch the buffer in that window. That's not expected for uselast.

[bogdan-nikitin]

Now I'm handling the disassembly buffer by checking the Vim variable b:dap_source_buf

[mfussenegger]

Now I'm handling the disassembly buffer by checking the Vim variable b:dap_source_buf

Thanks