fix: type errors

lua/cp/init.lua

@@ -42,7 +42,7 @@ end
 ---@param problem_id? string
 ---@param language? string
 local function setup_problem(contest_id, problem_id, language)
-  if not state.get_platform() then
+  if state.get_platform() == '' then
     logger.log('no platform set. run :CP <platform> <contest> first', vim.log.levels.ERROR)
     return
   end
@@ -222,7 +222,7 @@ local function toggle_run_panel(is_debug)
     return
   end
 
-  if not state.get_platform() then
+  if state.get_platform() == '' then
     logger.log(
       'No contest configured. Use :CP <platform> <contest> <problem> to set up first.',
       vim.log.levels.ERROR
@@ -665,7 +665,7 @@ end
 ---@param contest_id string
 ---@param language? string
 local function setup_contest(contest_id, language)
-  if not state.get_platform() then
+  if state.get_platform() == '' then
     logger.log('no platform set', vim.log.levels.ERROR)
     return false
   end

lua/cp/state.lua

@@ -1,8 +1,8 @@
 local M = {}
 
 local state = {
-  platform = nil,
-  contest_id = nil,
+  platform = '',
+  contest_id = '',
   problem_id = nil,
   test_cases = nil,
   run_panel_active = false,
@@ -66,12 +66,12 @@ function M.get_context()
 end
 
 function M.has_context()
-  return state.platform and state.contest_id
+  return state.platform ~= '' and state.contest_id ~= ''
 end
 
 function M.reset()
-  state.platform = nil
-  state.contest_id = nil
+  state.platform = ''
+  state.contest_id = ''
   state.problem_id = nil
   state.test_cases = nil
   state.run_panel_active = false