Only send HTML when using RTE when necessary

When there are no styled blocks or inline styles applied within blocks, just send text instead of HTML.

Also, don't add <br /> for the last <p> (the last block).

Fixes https://github.com/vector-im/riot-web/issues/3147

src/HtmlUtils.js

@@ -85,7 +85,6 @@ export function charactersToImageNode(alt, useSvg, ...unicode) {
 
 
 export function processHtmlForSending(html: string): string {
-
     const contentDiv = document.createElement('div');
     contentDiv.innerHTML = html;
 
@@ -94,10 +93,14 @@ export function processHtmlForSending(html: string): string {
     }
 
     let contentHTML = "";
-    for (let i=0; i<contentDiv.children.length; i++) {
+    for (let i=0; i < contentDiv.children.length; i++) {
         const element = contentDiv.children[i];
         if (element.tagName.toLowerCase() === 'p') {
-            contentHTML += element.innerHTML + '<br />';
+            contentHTML += element.innerHTML;
+            // Don't add a <br /> for the last <p>
+            if (i !== contentDiv.children.length - 1) {
+                contentHTML += '<br />';
+            }
         } else if (element.tagName.toLowerCase() === 'pre') {
             // Replace "<br>\n" with "\n" within `<pre>` tags because the <br> is
             // redundant. This is a workaround for a bug in draft-js-export-html: