Fix #1861: Crashing on "Show assembly load log" button click

ILSpy/Languages/CSharpLanguage.cs

@@ -300,7 +300,9 @@ namespace ICSharpCode.ILSpy
 			string line1 = Properties.Resources.WarningSomeAssemblyReference;
 			string line2 = Properties.Resources.PropertyManuallyMissingReferencesListLoadedAssemblies;
 			AddWarningMessage(module, output, line1, line2, Properties.Resources.ShowAssemblyLoad, Images.ViewCode, delegate {
-				MainWindow.Instance.SelectNode(MainWindow.Instance.FindTreeNode(module).Children.OfType<ReferenceFolderTreeNode>().First());
+				ILSpyTreeNode assemblyNode = MainWindow.Instance.FindTreeNode(module);
+				assemblyNode.EnsureLazyChildren();
+				MainWindow.Instance.SelectNode(assemblyNode.Children.OfType<ReferenceFolderTreeNode>().Single());
 			});
 		}