message: fix unlimited sheet contents height
diff: @@ -55,6 +55,7 @@ $control-color: rgba(255, 255, 255, 0.5);
  display: flex;
  flex-direction: column;
  position: relative;
  + max-height: calc(var(--viewport-height) - var(--header-height) - 8px);
  }
  .sheet-contents {
  