message: Fix line numbers when missing trailing newline
  _addLineNumbers expected code blocks to contain a trailing newline, but
  this is not always the case.
diff: @@ -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>';
  }
  }
  