Merge branch 'master' into 1.5

# Conflicts:
#	Content/Shaders/GI/DDGI.flax
#	Content/Shaders/GI/GlobalSurfaceAtlas.flax
#	Content/Shaders/TAA.flax
#	Content/Shaders/VolumetricFog.flax
#	Source/Editor/Utilities/Utils.cs

Source/Engine/Level/Actor.cs

@@ -123,6 +123,9 @@ namespace FlaxEngine
         /// <returns>The child actor.</returns>
         public Actor AddChild(Type type)
         {
+            if (type.IsAbstract)
+                return null;
+            
             var result = (Actor)New(type);
             result.SetParent(this, false, false);
             return result;
@@ -135,6 +138,9 @@ namespace FlaxEngine
         /// <returns>The child actor.</returns>
         public T AddChild<T>() where T : Actor
         {
+            if (typeof(T).IsAbstract)
+                return null;
+
             var result = New<T>();
             result.SetParent(this, false, false);
             return result;
@@ -172,6 +178,9 @@ namespace FlaxEngine
             var result = GetChild<T>();
             if (result == null)
             {
+                if (typeof(T).IsAbstract)
+                    return null;
+                
                 result = New<T>();
                 result.SetParent(this, false, false);
             }
@@ -185,6 +194,9 @@ namespace FlaxEngine
         /// <returns>The created script instance, null otherwise.</returns>
         public Script AddScript(Type type)
         {
+            if (type.IsAbstract)
+                return null;
+            
             var script = (Script)New(type);
             script.Parent = this;
             return script;
@@ -197,6 +209,9 @@ namespace FlaxEngine
         /// <returns>The created script instance, null otherwise.</returns>
         public T AddScript<T>() where T : Script
         {
+            if (typeof(T).IsAbstract)
+                return null;
+            
             var script = New<T>();
             script.Parent = this;
             return script;

Source/Engine/Level/Actor.h

@@ -207,6 +207,9 @@ public:
         T* result = (T*)GetChild(T::GetStaticClass());
         if (!result)
         {
+            if (T::GetStaticClass()->IsAbstract())
+                return nullptr;
+
             result = New<T>();
             result->SetParent(this, false, false);
         }

Source/Engine/Level/Level.cpp

@@ -176,6 +176,12 @@ bool LevelImpl::spawnActor(Actor* actor, Actor* parent)
         return true;
     }
 
+    if (actor->GetType().ManagedClass->IsAbstract())
+    {
+        Log::Exception(TEXT("Cannot spawn abstract actor type."));
+        return true;
+    }
+
     if (actor->Is<Scene>())
     {
         // Spawn scene