Clear the last of the nil checks

Guards now cover the statements that follow them, and a couple of reads
are restructured so the narrowing survives.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

exp_legacy/module/expcore/external.lua

@@ -14,7 +14,8 @@ end
 
 ]]
 
-local ext, var
+local ext --- @type table<string, any>
+local var --- @type table<string, any>
 local concat = table.concat
 
 local External = {}
@@ -29,12 +30,13 @@ end
 
 ]]
 function External.valid()
-    if storage.ext == nil then return false end
-    if ext == storage.ext and var == ext.var then
+    local stored = storage.ext
+    if stored == nil then return false end
+    if ext == stored and var == ext.var then
         return var ~= nil
     else
-        ext = storage.ext
-        var = ext.var
+        ext = stored
+        var = stored.var
         return var ~= nil
     end
 end

exp_legacy/module/modules/control/protection.lua

@@ -34,7 +34,7 @@ for _, config_key in ipairs{ "always_protected_names", "always_protected_types",
 end
 
 -- Require roles if a permission is assigned in the config
-local Roles
+local Roles --- @type table<string, any>
 if config.ignore_permission then
     Roles = require("modules.exp_legacy.expcore.roles") --- @dep expcore.roles
 end

exp_legacy/module/modules/control/spectate.lua

@@ -4,7 +4,7 @@ local Gui = require("modules/exp_gui")
 local Event = require("modules/exp_legacy/utils/event") --- @dep utils.event
 
 ----- Locals -----
-local follow_label -- Gui constructor
+local follow_label --- @type ExpElement Gui constructor
 local following = {}
 local spectating = {}
 local Public = {}

exp_legacy/module/modules/gui/warp-list.lua

@@ -673,7 +673,7 @@ warp_list_container = Gui.define("warp_list_container")
         -- Draw the scroll table for the warps
         local scroll_table = Gui.elements.scroll_table(container, 250, 3, "scroll")
         -- Set the scroll panel to always show the scrollbar (not doing this will result in a changing gui size)
-        scroll_table.parent.vertical_scroll_policy = "always"
+        assert(scroll_table.parent).vertical_scroll_policy = "always"
 
         -- Change the style of the scroll table
         local scroll_table_style = scroll_table.style
@@ -874,7 +874,7 @@ local function role_update_event(event)
     -- Check if user has permission to add warps
     local allow_add_warp = check_player_permissions(player, "allow_add_warp")
     -- Update container size depending on whether the player is allowed to add warps
-    frame.parent.style.width = allow_add_warp and 268 or 220
+    assert(frame.parent).style.width = allow_add_warp and 268 or 220
 
     -- Update the warps, in case the user can now edit them
     local scroll_table = frame.scroll.table