message: fix: show avatar for historical muc msg
diff: }
  }
  - .jsxc-chatmessage.jsxc-in {
  + .jsxc-chatmessage.jsxc-in,
  + .jsxc-chatmessage.jsxc-probably_in {
  margin-left: 50px;
  .jsxc-avatar {
  }
  }
  + .jsxc-chatmessage.jsxc-probably_in {
  + .jsxc-avatar {
  + filter: grayscale(1);
  + }
  + }
  +
  .jsxc-bar {
  .jsxc-avatar {
  @extend %muc-avatar-icon;
  