fix: cancel old render tasks on setup

If setup is called multiple times, we need to remove old render tasks so
they don't conflict with the new ones.

See #277

lua/dapui/init.lua

@@ -74,6 +74,8 @@ end
 ---@eval return require('dapui.config')._format_default()
 ---@param user_config? dapui.Config
 function dapui.setup(user_config)
+  util.stop_render_tasks()
+
   config.setup(user_config)
 
   local client = require("dapui.client")(dap.session)

lua/dapui/util.lua

@@ -5,11 +5,20 @@ local M = {}
 
 local api = async.api
 
+local render_tasks = {}
+
+function M.stop_render_tasks()
+  for _, task in ipairs(render_tasks) do
+    task.cancel()
+  end
+  render_tasks = {}
+end
+
 ---@return function
 function M.create_render_loop(render)
   local render_event = async.control.event()
 
-  async.run(function()
+  render_tasks[#render_tasks + 1] = async.run(function()
     while true do
       render_event.wait()
       render_event.clear()