Added guards in create object initialization to prevent memory leaks (#664)

src/bacnet/basic/object/mso.c

@@ -1220,5 +1220,7 @@ void Multistate_Output_Cleanup(void)
  */
 void Multistate_Output_Init(void)
 {
-    Object_List = Keylist_Create();
+    if (!Object_List) {
+        Object_List = Keylist_Create();
+    }
 }