Fix highlights on expanded lines.

[przepompownia]

• Don't pass invalid ns_id key to nvim_buf_set_extmark opts - it resulted with error (silenced by using pcall)
• Fix column number in the end of range of copied extmark
• Quick return if window id is invalid
• fix revealed line/column issues (related to different offset on vim.fn and vim.api methods)
• notify (debug level) about some errors (maybe not needed after above fixes)

[przepompownia]

master (window with no extmark copied):

df34cd0 (extmarks are copied but into incorrect position):

52f5c7a(extmarks are placed correctly):

[rcarriga]

Great thanks for the PR! 😄

[przepompownia]

Thanks for merging. For many months I couldn't find a good time to look in detail at what was happening there.