Fix LineDataEventAddon register call

This would only cause problems if we disposed the addon before xterm was disposed

src/vs/workbench/contrib/terminal/browser/addons/lineDataEventAddon.ts

@@ -22,13 +22,13 @@ export class LineDataEventAddon extends Disposable implements ITerminalAddon {
  activate(xterm: XTermTerminal) {
  this._xterm = xterm;
  // Fire onLineData when a line feed occurs, taking into account wrapped lines
- xterm.onLineFeed(() => {
+ this._register(xterm.onLineFeed(() => {
  const buffer = xterm.buffer;
  const newLine = buffer.active.getLine(buffer.active.baseY + buffer.active.cursorY);
  if (newLine && !newLine.isWrapped) {
  this._sendLineData(buffer.active, buffer.active.baseY + buffer.active.cursorY - 1);
  }
- });
+ }));
 
  // Fire onLineData when disposing object to flush last line
  this._register(toDisposable(() => {