fix(ts-context): clear context when buf has no ft/parser

closes #2344

Author: ibhagwan

lua/fzf-lua/previewer/builtin.lua

@@ -978,24 +978,32 @@ end
 
 function Previewer.base:update_ts_context()
   local bufnr = self.preview_bufnr
-  if not bufnr or not package.loaded["treesitter-context"] then return end
-  local ft = vim.b[bufnr] and vim.b[bufnr]._ft
-  if not ft
+  if not bufnr
       or not self.win
       or not self.win:validate_preview()
       or not self.treesitter.enabled
       or not self.treesitter.context
+      or not package.loaded["treesitter-context"]
   then
     return
   end
+  local ft = vim.b[bufnr] and vim.b[bufnr]._ft
+  if not ft then
+    TSContext.close(self.win.preview_winid)
+    return
+  end
   -- HACK: since TS async parsing commit we cannot guarantee the TSContext ranges as these will
   -- return empty unless parsing is complete and we have no access to the `on_parse` event
   -- https://github.com/neovim/neovim/commit/45e606b1fddbfeee8fe28385b5371ca6f2fba71b
   -- For more info see #1922
   local lang = vim.treesitter.language.get_lang(ft)
-  if not utils.has_ts_parser(lang) then return end
-  local parser = vim.treesitter.get_parser(self.preview_bufnr, lang)
-  if not parser then return end
+  if not utils.has_ts_parser(lang) then
+    TSContext.close(self.win.preview_winid)
+    return
+  end
+  local parser, err = vim.treesitter.get_parser(self.preview_bufnr, lang)
+  -- should never fail since `utils.has_ts_parser` returned true
+  assert(parser, "'vim.treesitter.get_parser' err: " .. tostring(err))
   local context_updated
   TSContext.zindex = self.win.winopts.zindex + 20
   for _, t in ipairs({ 0, 20, 50, 100 }) do