Fix using ASDisplayNodePerformBlockOnEveryNode if node is loaded and has shouldRasterizeDescendants enabled (#2179)

We don't call the block on every subnode if the node that is passed in ASDisplayNodePerformBlockOnEveryNode has shouldRasterizeDescendants enabled as it tries to iterate through the sublayer hierarchy, but there are no sublayers

AsyncDisplayKit/ASDisplayNodeExtras.mm

@@ -54,7 +54,7 @@ extern void ASDisplayNodePerformBlockOnEveryNode(CALayer *layer, ASDisplayNode *
     layer = node.layer;
   }
   
-  if (layer) {
+  if (layer && node.shouldRasterizeDescendants == NO) {
     /// NOTE: The docs say `sublayers` returns a copy, but it does not.
     /// See: http://stackoverflow.com/questions/14854480/collection-calayerarray-0x1ed8faa0-was-mutated-while-being-enumerated
     for (CALayer *sublayer in [[layer sublayers] copy]) {

AsyncDisplayKitTests/ASDisplayNodeTests.m

@@ -1964,4 +1964,26 @@ static bool stringContainsPointer(NSString *description, id p) {
   XCTAssertNoThrow([nodeView removeFromSuperview]);
 }
 
+
+- (void)testThatSubnodeGetsInterfaceStateSetIfRasterized
+{
+  ASTestDisplayNode *node = [[ASTestDisplayNode alloc] init];
+  node.name = @"Node";
+  node.shouldRasterizeDescendants = YES;
+  
+  ASTestDisplayNode *subnode = [[ASTestDisplayNode alloc] init];
+  subnode.name = @"Subnode";
+  [node addSubnode:subnode];
+  
+  [node view]; // Node needs to be loaded
+  
+  [node enterInterfaceState:ASInterfaceStateFetchData];
+  
+  
+  XCTAssertTrue((node.interfaceState & ASInterfaceStateFetchData) == ASInterfaceStateFetchData);
+  XCTAssertTrue((subnode.interfaceState & ASInterfaceStateFetchData) == ASInterfaceStateFetchData);
+  XCTAssertTrue(node.hasFetchedData);
+  XCTAssertTrue(subnode.hasFetchedData);
+}
+
 @end