fix(files): remove invalid window from explorer.windows

lua/mini/files.lua

@@ -1544,14 +1544,8 @@ H.explorer_refresh = function(explorer, opts)
     explorer = H.explorer_sync_cursor_and_branch(explorer, depth)
   end
 
-  -- Unregister windows from showed buffers, as they might get outdated
-  for _, win_id in ipairs(explorer.windows) do
-    -- NOTE: window can be invalid if it was showing buffer that was deleted
-    if H.is_valid_win(win_id) then
-      local buf_id = vim.api.nvim_win_get_buf(win_id)
-      H.opened_buffers[buf_id].win_id = nil
-    end
-  end
+  -- Unregister windows from shown buffers, as they might get outdated
+  explorer = H.explorer_unregister_windows(explorer)
 
   -- Compute depth range which is possible to show in current window
   local depth_range = H.compute_visible_depth_range(explorer, explorer.opts)
@@ -1684,6 +1678,20 @@ H.explorer_sync_cursor_and_branch = function(explorer, depth)
   return explorer
 end
 
+H.explorer_unregister_windows = function(explorer)
+  local valid_windows = {}
+  for i, win_id in ipairs(explorer.windows) do
+    -- NOTE: window can be invalid if it was showing buffer that was deleted
+    if H.is_valid_win(win_id) then
+      local buf_id = vim.api.nvim_win_get_buf(win_id)
+      H.opened_buffers[buf_id].win_id = nil
+      table.insert(valid_windows, win_id)
+    end
+  end
+  explorer.windows = valid_windows
+  return explorer
+end
+
 H.explorer_go_in_range = function(explorer, buf_id, from_line, to_line)
   -- Compute which entries to go in: all files and only last directory
   local files, path, line = {}, nil, nil

tests/test_files.lua

@@ -5733,6 +5733,19 @@ T['Events']['`MiniFilesWindowUpdate` can customize internally set window config
   expect_screenshot()
 end
 
+T['Events']['MiniFilesWindowUpdate with preview works with `get_explorer_state()` after `undo`'] = function()
+  child.lua('MiniFiles.config.windows.preview = true')
+  child.lua([[
+    vim.api.nvim_create_autocmd('User', {
+      pattern = 'MiniFilesWindowUpdate',
+      callback = function() MiniFiles.get_explorer_state() end
+    })
+  ]])
+  open()
+  type_keys('o', '<Esc>', 'u')
+  eq(#get_explorer_state().windows, 2)
+end
+
 T['Events']['`MiniFilesActionCreate` triggers'] = function()
   track_event('MiniFilesActionCreate')