handleEnterKeyPress = function(event, composer) {
    if (composer.config.useLineBreaks && !event.shiftKey && !event.ctrlKey) {
      // Fixes some misbehaviours of enters in linebreaks mode (natively a bit unsupported feature)

      var breakNodes = "p, pre, div, blockquote",
          caretInfo, parent, txtNode;

      if (composer.selection.isCollapsed()) {
        if (actions.doLineBreaksModeEnterWithCaret(composer)) {
          event.preventDefault();
        }
      }
    }

    if (browser.hasCaretAtLinkEndInsertionProblems() && composer.selection.caretIsInTheEndOfNode()) {
      var target = composer.selection.getSelectedNode(true),
          targetEl = (target && target.nodeType === 3) ? target.parentNode : target, // target guaranteed to be an Element
          invisibleSpace, space;

      if (targetEl && targetEl.closest('a') && target.nodeType === 3 && target === targetEl.lastChild) {
        // Seems like enter was pressed and caret was at the end of link node
        // This means user wants to escape the link now (caret is last in link node too).
        composer.selection.setAfter(targetEl);
      }
    }
  }
when the editor is empty in useLineBreaks = false mode, preserve
the default value in it which is <p><br></p>