Do not show non-image attachment in a <img> tag. Fixes #3215 (#3311)

public/less/_repository.less

@@ -463,6 +463,13 @@
 							margin: 0;
 							vertical-align: middle;
 						}
+						span.ui.image {
+							font-size: 8vw;
+							color: #000000;
+						}
+						span.ui.image:hover {
+							color: #000000;
+						}
 					}
 				}