Nativescript: Background color applied twice in labels with `<span>`s

[tralves]

Environment
Irrelevant. Occurs both on Android and iOS. Replicable in the playground.

Describe the bug
When applying a background to a label with a formatted string, the background is re-applied in the inner <span>s. This is a problem when we have a semi-transparent background, as you can see here:

To Reproduce
Run the sample here: https://play.nativescript.org/?template=play-vue&id=x0j7SP

Expected behavior
The background should only be applied to the label, and not in the inner span again.

Sample project
https://play.nativescript.org/?template=play-vue&id=x0j7SP&v=2

Additional context

---

Want to back this issue? Post a bounty on it! We accept bounties via Bountysource.

[tralves]

BTW, there is an easy workaround: set the background color of the span to transparent:

<Label textWrap="true" class="h2 description-label">
  <FormattedString>
    <Span text="Play with NativeScript!" backgroundColor="transparent"></Span>
   </FormattedString>
 </Label>