fix: LualineRenameTab crashing lualine

fixes https://github.com/nvim-lualine/lualine.nvim/pull/574#pullrequestreview-874872853

Issue was neovim's tabpage handle used by rpc-api isn't same as tab no
in viml.
Now the tabpage handle is stores in self.tabId and tab no is stored in
self.tabnr in `Tab` so any can be used when necessary.

lua/lualine/components/tabs/init.lua

@@ -57,8 +57,8 @@ end
 function M:update_status()
   local data = {}
   local tabs = {}
-  for t = 1, vim.fn.tabpagenr('$') do
-    tabs[#tabs + 1] = Tab { tabnr = t, options = self.options, highlights = self.highlights }
+  for nr, id in ipairs(vim.api.nvim_list_tabpages()) do
+    tabs[#tabs + 1] = Tab { tabId = id, tabnr = nr, options = self.options, highlights = self.highlights }
   end
   -- mark the first, last, current, before current, after current tabpages
   -- for rendering
@@ -93,7 +93,12 @@ function M:update_status()
   -- start drawing from current tab and draw left and right of it until
   -- all tabpages are drawn or max_length has been reached.
   if current_tab == nil then -- maybe redundent code
-    local t = Tab { tabnr = vim.fn.tabpagenr(), options = self.options, highlights = self.highlights }
+    local t = Tab {
+      tabId = vim.api.nvim_get_current_tabpage(),
+      tabnr = vim.fn.tabpagenr(),
+      options = self.options,
+      highlights = self.highlights,
+    }
     t.current = true
     t.last = true
     data[#data + 1] = t:render()

lua/lualine/components/tabs/tab.lua

@@ -6,6 +6,7 @@ local Tab = require('lualine.utils.class'):extend()
 function Tab:init(opts)
   assert(opts.tabnr, 'Cannot create Tab without tabnr')
   self.tabnr = opts.tabnr
+  self.tabId = opts.tabId
   self.options = opts.options
   self.highlights = opts.highlights
 end
@@ -14,7 +15,7 @@ end
 --- of the tab.
 ---@return string
 function Tab:label()
-  local custom_tabname = vim.t[self.tabnr].tabname
+  local custom_tabname = vim.t[self.tabId].tabname
   if custom_tabname and custom_tabname ~= '' then
     return custom_tabname
   end