fix: #25 Fixes vim:E976 error when cursor is on a blob.

[rpopic2]

• How to reproduce the original error:
  Error executing lua callback: Vim:E976: using Blob as a String #25
  Open any binary file, move cursor on a blob(blue characters starting with ^), throws vim:E976.
  This error is thrown when blob is provided for function vim.fn.matchstr(), instead of a string.
• What changes I've made:
  • In function matchadd() (line 12),
  • Check whether the current line is a blob, seeing if fn.type(line) is a vim.v.t_blob.
  • If it is a blob, return early from matchadd()
• Test results:
  I tried reproducing the bug as I mentioned above, and it was fixed.
  Testing environment: MacOS Ventura 13.1, Apple M2, nvim v0.8.3

[Forsigg]

Hello! I see that PR approved, but not merged. I also get this error from issue. @alanchenvon please merge that PR if all ok. And thanks @rpopic2 for that fix!

[ya2s]

Thanks for working on this fix. I reviewed the patch with Issue #25 in mind, and I think we should adjust a few points before merge:

1. Early return on blob can leave stale highlight

• The new if fn.type(line) == vim.v.t_blob then return end exits before deleting existing w.cursorword_id.
• If a previous match exists, it may remain visible when moving onto blob lines.
• Suggestion: clear existing cursorword_id first, then return for blob lines.

2. cursorword == "~" is a special-case workaround, not a root fix

• Excluding only ~ still leaves other regexp meta chars (*, +, [, |, etc.) as potential failures.
• Suggestion: make pattern construction robust (escape dynamic word / very nomagic) instead of blacklisting specific symbols.

The blob type guard is a good direction, but these changes would make the fix safer.