adjust blur effects to new conditions, fixes #2069

Closes #2069

Merge request studip/studip!1355

resources/assets/stylesheets/less/globalsearch.less

@@ -306,7 +306,10 @@ html:not(.size-large) {
             z-index: 0;
         }
 
-        #layout_page {
+        #flex-header,
+        #layout_page,
+        #scroll-to-top,
+        #layout_footer {
             position: relative;
             filter: blur(1px);