[LYN-4544] Fixing thumbnail crashing on bad data

Signed-off-by: mnaumov <mnaumov@amazon.com>

Gems/AtomLyIntegration/CommonFeatures/Code/Source/Thumbnails/Rendering/ThumbnailRendererSteps/CaptureStep.cpp

@@ -91,6 +91,13 @@ namespace AZ
 
                     RPI::AttachmentReadback::CallbackFunction readbackCallback = [&](const RPI::AttachmentReadback::ReadbackResult& result)
                     {
+                        if (!result.m_dataBuffer)
+                        {
+                            AzToolsFramework::Thumbnailer::ThumbnailerRendererNotificationBus::Event(
+                                m_context->GetData()->m_thumbnailKeyRendered,
+                                &AzToolsFramework::Thumbnailer::ThumbnailerRendererNotifications::ThumbnailFailedToRender);
+                            return;
+                        }
                         uchar* data = result.m_dataBuffer.get()->data();
                         QImage image(
                             data, result.m_imageDescriptor.m_size.m_width, result.m_imageDescriptor.m_size.m_height, QImage::Format_RGBA8888);