-IDManager reserve EntityID(0) as empty

-fixed bug with events called on destroyed entities (crash)
-don't call event on system for unsupported entity
-added "entity_id" property to EntitiesData

source/ecs/id_manager.d

@@ -136,7 +136,9 @@ begin:
     */
     export bool isExist(EntityID id) nothrow @nogc
     {
+        if(id.id >= m_ids_array.length)return false;
         Data* data = &m_ids_array[id.id];
+        if(data.entity is null)return false;
         return data.counter == id.counter;
     }
 
@@ -151,6 +153,9 @@ begin:
 
         add_mutex = Mallocator.make!Mutex();
         add_mutex.initialize();
+
+        getNewID();
+        optimize();
     }
 
     void deinitialize() @trusted @nogc nothrow
@@ -243,23 +248,31 @@ private:
 unittest
 {
     IDManager manager;
+    manager.initialize();
     EntityID id1 = manager.getNewID();
     EntityID id2 = manager.getNewID();
     EntityID id3 = manager.getNewID();
 
-    assert(id1 == EntityID(0, 1));
-    assert(id2 == EntityID(1, 1));
-    assert(id3 == EntityID(2, 1));
+    assert(id1 == EntityID(1, 0));
+    assert(id2 == EntityID(2, 0));
+    assert(id3 == EntityID(3, 0));
 
+    manager.optimize();
     manager.releaseID(id2);
     manager.releaseID(id1);
 
     id2 = manager.getNewID();
     id1 = manager.getNewID();
 
-    assert(id1 == EntityID(1, 2));
-    assert(id2 == EntityID(0, 2));
-    assert(id3 == EntityID(2, 1));
+    Entity e;
+    e.id = id3;
+    manager.update(e);
+
+    assert(id1 == EntityID(2, 1));
+    assert(id2 == EntityID(1, 1));
+    assert(id3 == EntityID(3, 0));
     assert(manager.isExist(id3));
-    assert(!manager.isExist(EntityID(0, 1)));
+    assert(!manager.isExist(EntityID(1, 0)));
+    assert(!manager.isExist(EntityID(0, 0)));
+    manager.deinitialize();
 }