Fix game crash on existing save

changelog.txt

@@ -1,4 +1,9 @@
 ---------------------------------------------------------------------------------------------------
+Version: 1.1.2
+Date: 2021-03-28
+  Bugfixes:
+    - Added migration to add car index to existing saves
+---------------------------------------------------------------------------------------------------
 Version: 1.1.1
 Date: 2021-03-28
   Changes:

control.lua

@@ -2,7 +2,7 @@
 --This mod scans the map for cars and gun-turrets and places alerts when they are low. 
 
 script.on_init(function (event)
-	-- turret index init
+	-- car and turret index init
 	global.turret_entities = {}
 	global.car_entities = {}
 end)

info.json

@@ -1,6 +1,6 @@
 {
     "name": "Gun_Turret_Alerts",
-    "version": "1.1.1",
+    "version": "1.1.2",
     "title": "Ammo Alerts",
     "author": "Wyrrrd",
     "factorio_version": "1.1",

migrations/1.1.2.lua

@@ -0,0 +1,4 @@
+script.on_configuration_changed(function (event)
+	-- car index init fix
+	global.car_entities = {}
+end)