Added comment to overlay

src/styles/_content.scss

@@ -105,6 +105,7 @@
 		background: linear-gradient(to bottom, rgba(0,0,0,0) 0%, rgba(0,0,0,0) 60%, rgba(0,0,0,0.5) 80%, rgba(0,0,0,0.9) 100%);
 	}
 
+	// No overlay for empty albums
 	.album img[data-type^='nonretina'] + .overlay {
 		background: rgba(0, 0, 0, 0.2);
 	}