Move null check

Author: umberto-sonnino

flare_flutter/lib/flare.dart

@@ -796,17 +796,16 @@ class FlutterActorArtboard extends ActorArtboard {
   FlutterActorArtboard(FlutterActor actor) : super(actor);
 
   void draw(ui.Canvas canvas) {
-    if (drawableNodes == null || drawableNodes.isEmpty) {
-      return;
-    }
     if (clipContents) {
       canvas.save();
       AABB aabb = artboardAABB();
       canvas.clipRect(Rect.fromLTRB(aabb[0], aabb[1], aabb[2], aabb[3]));
     }
-    for (final ActorDrawable drawable in drawableNodes) {
-      if (drawable is FlutterActorDrawable) {
-        (drawable as FlutterActorDrawable).draw(canvas);
+    if (drawableNodes != null) {
+      for (final ActorDrawable drawable in drawableNodes) {
+        if (drawable is FlutterActorDrawable) {
+          (drawable as FlutterActorDrawable).draw(canvas);
+        }
       }
     }
     if (clipContents) {