Fix CSS for modal image when the image is smaller

Author: bep

assets/css/gallerydeluxe/styles.css

@@ -29,12 +29,16 @@
 
 /* Modal Content (image) */
 .gd-modal-content {
-  position: absolute;
-  display: block;
-  overflow: hidden;
-  object-fit: contain;
   max-width: 100%;
   max-height: 100%;
+  bottom: 0;
+  left: 0;
+  margin: auto;
+  overflow: auto;
+  position: fixed;
+  right: 0;
+  top: 0;
+  object-fit: contain;
 }
 
 .gd-modal-content.gd-modal-thumbnail {