RepoEditor: Fix empty state for image blob view.

app/assets/stylesheets/pages/repo.scss

@@ -84,6 +84,13 @@
       }
     }
 
+    .blob-no-preview {
+      .vertical-center {
+        justify-content: center;
+        width: 100%;
+      }
+    }
+
     &.edit-mode {
       .blob-viewer-container {
         overflow: hidden;

app/views/projects/blob/viewers/_download.html.haml

 .file-content.blob_file.blob-no-preview
-  .center
+  .center.render-error.vertical-center
     = link_to blob_raw_path do
       %h1.light
         = icon('download')