Add white background for no readme container

CHANGELOG

@@ -9,6 +9,7 @@ v 8.12.0 (unreleased)
   - Set path for all JavaScript cookies to honor GitLab's subdirectory setting !5627 (Mike Greiling)
   - Add hover color to emoji icon (ClemMakesApps)
   - Fix branches page dropdown sort alignment (ClemMakesApps)
+  - Add white background for no readme container (ClemMakesApps)
   - Optimistic locking for Issues and Merge Requests (title and description overriding prevention)
   - Add `wiki_page_events` to project hook APIs (Ben Boeckel)
   - Remove Gitorious import

app/assets/stylesheets/pages/projects.scss

@@ -600,7 +600,13 @@ pre.light-well {
   }
 }
 
-.project-show-readme .readme-holder {
+.project-show-readme {
+  .row-content-block {
+    background-color: inherit;
+    border: none;
+  }
+
+  .readme-holder {
     padding: $gl-padding 0;
     border-top: 0;
 
@@ -613,6 +619,7 @@ pre.light-well {
       border-bottom: none;
       padding: 0;
     }
+  }
 }
 
 .git-clone-holder {