remove close button

res/include/script/file_viewer/Viewer.js

@@ -25,12 +25,6 @@ function Viewer(type, viewToken, data) {
 		this.toolbar.toggle()
 	}
 
-	// The close button only works if the window has an opener. So we hide
-	// the button if it does not
-	if (window.opener === null && window.history.length !== 1) {
-		document.getElementById("button_close_file_viewer").remove()
-	}
-
 	if (type === "file") {
 		this.isFile = true
 		this.title = data.name