fix(diagnostic): handle stale diagnostic extmark ids #38060

Problem:
If a server is slow with catching up, there can be stale diagnostics
for deleted lines. Then if a user uses `jump` it can error like:

    E5108: Lua: ...runtime/lua/vim/diagnostic.lua:670: attempt to index a nil value
    stack traceback:
            ...runtime/lua/vim/diagnostic.lua:670: in function 'get_logical_pos'
            ...runtime/lua/vim/diagnostic.lua:687: in function 'diagnostic_lines'
            ...runtime/lua/vim/diagnostic.lua:1122: in function 'next_diagnostic'
            ...runtime/lua/vim/diagnostic.lua:1665: in function 'jump'

Solution:
Fallback to diagnostic location. That's better than the failure.

0 files changed, 0 insertions, 0 deletions