Null checks

src/Drawie

@@ -1 +1 @@
-Subproject commit bfdfb763a00e7bcfa2e650899e58d5d42e388457
+Subproject commit 8f1ba3da5b369736aed99288e46487c05e887d14

src/PixiEditor.ChangeableDocument/Changeables/Graph/Nodes/CombineSeparate/SeparateChannelsNode.cs

@@ -69,6 +69,9 @@ public class SeparateChannelsNode : Node, IRenderInput, IPreviewRenderable
 
     private void Paint(RenderContext context, DrawingSurface drawingSurface, ColorFilter colorFilter, ColorFilter grayscaleFilter)
     {
+        if(Image.Value == null)
+            return;
+        
         bool grayscale = Grayscale.Value;
         
         ColorFilter filter = grayscale ? grayscaleFilter : colorFilter; 

src/PixiEditor/ViewModels/Document/NodeGraphViewModel.cs

@@ -301,7 +301,7 @@ internal class NodeGraphViewModel : ViewModelBase, INodeGraphHandler
 
         if (input == null && output != null)
         {
-            input = output.ConnectedInputs.FirstOrDefault();
+            input = output.ConnectedInputs?.FirstOrDefault();
             output = null;
         }