Fix line numbers when missing trailing newline

_addLineNumbers expected code blocks to contain a trailing newline, but
this is not always the case.

Signed-off-by: Robin Townsend <[email protected]>

Author: robintown

src/components/views/messages/TextualBody.js

@@ -216,12 +216,12 @@ export default class TextualBody extends React.Component {
     }
 
     _addLineNumbers(pre) {
+        // Calculate number of lines in pre
+        const number = pre.innerHTML.replace(/\n(<\/code>)?$/, "").split(/\n/).length;
         pre.innerHTML = '<span class="mx_EventTile_lineNumbers"></span>' + pre.innerHTML + '<span></span>';
         const lineNumbers = pre.getElementsByClassName("mx_EventTile_lineNumbers")[0];
-        // Calculate number of lines in pre
-        const number = pre.innerHTML.split(/\n/).length;
         // Iterate through lines starting with 1 (number of the first line is 1)
-        for (let i = 1; i < number; i++) {
+        for (let i = 1; i <= number; i++) {
             lineNumbers.innerHTML += '<span class="mx_EventTile_lineNumber">' + i + '</span>';
         }
     }