Added guard for some object inits to prevent memory leak by misuse (#662)

Co-authored-by: Nik Schewtschuk <nikonlinee@gmail.com>

src/bacnet/basic/object/ao.c

@@ -1279,5 +1279,7 @@ void Analog_Output_Cleanup(void)
  */
 void Analog_Output_Init(void)
 {
-    Object_List = Keylist_Create();
+    if (!Object_List) {
+        Object_List = Keylist_Create();
+    }
 }