Fix public page footer position in IE

The content element needs hasLayout, so triggering it with a display
attribute.

Without this, the #content element's height would be as high as the
window's height instead of adjusting itself to its contents' height.

apps/files_sharing/css/public.css

@@ -3,6 +3,11 @@
 	min-height: calc(100vh - 120px);
 }
 
+/* force layout to make sure the content element's height matches its contents' height */
+.ie #content {
+	display: inline-block;
+}
+
 #preview {
 	background: #fff;
 	text-align: center;