Add comments & remove redundant check

src/HtmlUtils.js

@@ -365,6 +365,11 @@ export function bodyToHtml(content, highlights, opts) {
 }
 
 function addCodeCopyButton(safeBody) {
+    // Adds 'copy' buttons to pre blocks
+    // Note that this only manipulates the markup to add the buttons:
+    // we need to add the event handlers once the nodes are in the DOM
+    // since we can't save functions in the markup.
+    // This is done in TextualBody
     const el = document.createElement("div");
     el.innerHTML = safeBody;
     const codeBlocks = Array.from(el.getElementsByTagName("pre"));

src/components/views/messages/TextualBody.js

@@ -94,8 +94,8 @@ module.exports = React.createClass({
                     }
                 }, 10);
             }
+            // add event handlers to the 'copy code' buttons
             const buttons = ReactDOM.findDOMNode(this).getElementsByClassName("mx_EventTile_copyButton");
-            if (buttons.length > 0) {
             for (let i = 0; i < buttons.length; i++) {
                 buttons[i].onclick = (e) => {
                     const copyCode = buttons[i].parentNode.getElementsByTagName("code")[0];
@@ -103,7 +103,6 @@ module.exports = React.createClass({
                 };
             }
         }
-        }
     },
 
     componentDidUpdate: function() {